This dissertation has been
microfilmed exactly as received
64-10,641
GABRIELSON, James Earl, 1934POTASSIUM NITRATE FROM NITRIC ACID AND
POTASSIUM CHLORIDE.
I
Iowa State University of Science and Technology
Ph.D., 1964
Engineering, chemical
University Microfilms, Inc., Ann Arbor, Michigan
POTASSIUM NITRATE FROM NITRIC ACID
AND POTASSIUM CHLORIDE
by
James Earl Gabrielson
A Dissertation Submitted to the
Graduate Faculty in Partial Fulfillment
The Requirements for the Degree of
DOCTOR OF PHILOSOPHY
Major Subject:
Chemical Engineering
Approved:
Signature was redacted for privacy.
In Charge of Major Work
Signature was redacted for privacy.
Head of Major Department
Signature was redacted for privacy.
DeMrprGraduâtSTollege^
Iowa State University
Of Science and Technology
Ames, Iowa
1964
il
TABLE OF CONTENTS
Page
ABSTRACT
iv
INTRODUCTION
1
LITERATURE REVIEW
3
History of Potassium Nitrate
3
Present Supply and Use of Potassium Nitrate
4
Need for Potassium Nitrate as a Fertilizer Material
5
Chlorine Demand
7
Reaction between Potassium Chloride and Nitric Acid
8
Patented Processes
9
Production of Potassium Nitrate at Vicksburg
13
Analysis
13
Gas Chromatography
13
Solubility of KC1 and KNOg in Water
15
GAS CHROMATOGRAPHY
19
Introduction
19
Gas-Solid Chromatography
Silica gel
Glass beads
Molecular sieves
Alumina
19
19
20
21
21
Gas Liquid Partition Chromatography
Aroclor 1232 on Halaport F
1, 2, 3 tris (2-cyanoethoxy) propane on Chromosorb P
Dimethyl phthalate on Chromosorb W
Triacetin on non-acid washed Chromosorb P
22
22
22
22
23
BATCH STUDIES
30
Equipment and Procedures
30
Analytical Procedures
33
Results and Discussion
33
SOLUBILITY STUDIES
38
iii
Page
Technique
Laboratory
Analytical
38
38
38
Results and Discussion
Mutual solubility of KC1 and KNO3
Solubility of KNO3 in solutions not saturated in KC1
39
39
42
CONTINUOUS RUNS
49
Runs without Supernatant Liquid Return
Equipment
Procedure and difficulties
Results and discussion
49
49
49
50
Runs with Crystallizer
Equipment and procedure
Results and discussion
55
55
59
Runs with Final Equipment Modifications
Equipment and procedures
Results and discussion
62
62
65
PROPOSED PROCESS
85
Cost Analysis for Commercial Process
85
Corrosion Study
88
Pilot Plant
89
CONCLUSIONS
92
RECOMMENDATIONS
94
LITERATURE CITED
95
ACKNOWLEDGEMENTS
99
APPENDIX A.
NELSON'S METHOD FOR DETERMINATION OF NITROGEN
100
APPENDIX B.
WOLF AND SCHIER GAS ANALYSIS
APPENDIX C.
OUTLINE OF CALCULATION OF COEFFICIENTS FOR RATE
CONCENTRATION RELATIONSHIP
'
105
107
ABSTRACT
i
This study was concerned with the development of a process for
the production of potassium nitrate for use as a fertilizer material.
The process uses KC1 and 60% HNO3 as the starting materials and the
intended co-product is Cl2.
From information in the literature it
was decided to react the KC1 directly with HNO3 simply by mixing the
two rather than using some other scheme such as employing an organic
solvent or vaporizing the HNO3 and using a gas-solid reaction. The
work was carried out in equipment constructed of glass.
The analysis, by gas chromatography, of the gaseous products of
the reaction mixed with air was studied.
Both gas solid chromatography
and gas liquid partition chromatography methods were examined.
While
none of the gas solid chromatographic methods gave encouraging results
several gas liquid partition chromatography system results were en­
couraging.
Air, CI2 and N0C1 were separated using a column packed with
triacetin on non-acid washed Chromosorb P. This system was used to
analyze the gases from a continuous reactor.
The reaction of KC1 with 60% HNO3 was first studied in batch
equipment. The reactor was kept in a constant temperature bath or in
some studies the reaction products were heated to dryness with a
flame.
The gases were reacted with various reagents in absorbers and
these reagents were later analyzed to find the nature of the gases
evolved.
The gases were found to be CI2 and N0C1.
The solid residues
were found to contain excessive amounts of chloride ions.
For this
reason, a batch reaction is not a satisfactory method to produce KNO3.
To find if it were possible to fractionally crystallize KNO3 from
aqueous nitric acid solutions containing KC1 and KNO3 a study was made
of the mutual solubility of these two salts in such solutions.
The
solubility studies were performed at 0, 16, 30, 45 and 60° C. and
various acid-water ratios.
Also a study of the solubility of KNO3 in
solutions of 0.3 gm HNO3 per gm HgO with controlled amounts of KC1 was
carried out at 30° C.
These studies showed that the KNO3 solubility
in such solutions changed markedly with temperature while the KC1
solubility did not change very much over the range of temperature
studied.
Therefore, it was found that it was possible to fractionally
crystallize KNO3 from aqueous nitric acid solutions containing KC1 and
KNO3.
To demonstrate the final process, equipment was set up to conI
tinuously react KC1 and HNO3, withdraw liquid from the reactor, frac­
tionally crystallize KNO3, and continuously remove the gaseous products.
This procedure produced solid KNO3 which contained no solid KC1.
The
only impurities in the KNO3 were from the mother liquor which adhered
to the crystals. The reaction was found to proceed more rapidly as
the temperature or the concentration of the reactants was increased.
INTRODUCTION
There are three primary plant nutrients, nitrogen (N), phosphate
(P2O5) and potash (K2O).
erly.
Plants need all three of these to grow prop­
Numerous other elements are also needed in lesser amounts for
satisfactory plant growth.
However, the primary nutrients are de­
pleted from almost all soils by continuous cropping.
Then for satis­
factory crop growth these nutrients must be replaced with naturallyoccurring or chemically produced fertilizer materials.
Approximately 93% of the K]0 applied as fertilizer in this
country is applied as potassium chloride (KC1) (37).
With the ex­
ception of specialized crops, one potash fertilizer is as effective as
any other as a source of potash for the plant. Tobacco is one example
of a crop sensitive to chlorides; quantities of K20 in excess of 30 to
40 lb/acre as chloride are harmful to the tobacco burning quality (37).
An alternate source of potassium is needed for tobacco and other
chloride sensitive crops.
Two forms of K^O are immediately brought to
mind, potassium sulfate (K2SO4) and potassium nitrate (KNO3). Potassium
sulfate is used to a limited extent while KNO3 has hardly been used at
all.
Presently one facility for producing KNO3 is known to exist in
this country (33). However, little information has been divulged about
the process (33).
Additional work on the development of a process for
the production of KNO3 seemed important.
The purpose of this investigation was to develop a KNO3 process.
2
Early in the work it was decided that KC1 and nitric acid (HNO3) would
be the reactants and that the most desirable co-product would be
elemental chlorine (CI2)•
Initially the KC1 was reacted directly
with HNO3 on a batch basis.
much KC1.
However, the solid product contained too
Published solubility curves for KC1 and KNO3 in water indi­
cated that a fractional crystallization process for KNO3 might be
possible and a study of the mutual solubility of KNO3 and KC1 in
aqueous HNO3 solutions tended to confirm this possibility.
Following
the solubility study a continuous fractional crystallization process
for KNO3 was investigated using glass equipment.
.3
LITERATURE SURVEY
History of Potassium Nitrate
Mehring et_ al_. (30) gave a brief history of the supply of po­
tassium nitrate (KNO3). The world supply was formerly derived from
incrustations on the soils around heavily populated areas in tropical
countries, notably, Ceylon, India, Egypt and Mexico.
Its presence is
due to the decomposition of organic matter by nitrifying organisms
in soil containing soluble potassium compounds.
Evaporation of soil
moisture causes the salt to concentrate at the surface.
When used as
a source of KNO3 a thin layer of soil is scraped up at frequent inter­
vals and extracted with boiling water.
The yield of crude KNO3 is 2
to 8% of the weight of soil scrapings.
During the Crimean War the demand for KNO3 for the manufacture of
gunpowder became so great that artificial saltpeter plantations were
created.
Garbage, animal refuse, and other decaying organic matter
were mixed with limestone or old plaster, wetted with urine and
allowed to ferment in piles protected from the rain.
After complete
decomposition, which required a year or two in northern Europe, the
piles were mixed with hardwood ashes and the KNO3 extracted.
yield was about 5 kg of KNO3 per cubic meter.
The
For many years European
governments permitted their subjects to pay taxes with saltpeter (KNO3)
and this practice was quite common among the peasants.
According to Russel (38) the use of KNO3 as a fertilizer was
4
first suggested by Glauber in 1656.
Potassium nitrate was used by
Home in the first pot experiments ever recorded and by Liebig and
Lowes and Gilbert in their all important work (38).
Mehring and his
co-workers (30) report that in the middle 17th century Digby discussed
the value of KNO3 in what is said to be the earliest record of actual
use of artificial fertilizers as distinct from decaying organic matter.
Present Supply and Use of Potassium-Nitrate
Kirk and Othmer (26) indicate that a small amount of KNO3 may
presently come from natural deposits.
However, they state that most
of it is made by taking advantage of the solubility relationships in
the system Kd-NaNC^-H^O.
In aqueous solution, the solubilities of
potassium chloride (KCl), and sodium nitrate (NaNC>3) increase
KNO3,
markedly with temperature, while that of the fourth possible single
salt of the system, sodium chloride, (NaCl) changes little.
Sodium
nitrate and KCl are dissolved in hot water to form a concentrated
solution.
The solution is evaporated to just below the solubility
limit of KNO3.
The NaCl crystals formed during the evaporation are
removed and the solution cooled.
Potassium nitrate is less soluble
than either NaNOs of KCl, and hence is obtained as the low-temperature
crop.
Potassium nitrate is used in the manufacture of some matches and
in various^pyrotechnics both of which make use of the oxidizing power
of the nitrate.
Other uses of KNO3 include the manufacture of certain
5
types of glass and ceramic glazes, meat curing, pickling, and in medi­
cine.
A mixture of 55% KNO3 and 45% NaNOg melts at 220° C. and makes
a convenient high-temperature liquid bath if contamination with organic
materials is avoided (26).
Need for Potassium Nitrate as a Fertilizer Material
McCants (29) has written a review of the status of KNO3 as a possi­
ble fertilizer.
While there is no difference between the chloride,
sulfate and nitrate salts of potassium insofar as the potassium ion
is concerned, there may be a difference on plant response due to the
associated ion.
For example, the use of KCl on a number of crops is
restricted because of the adverse effect of excessive chlorine on crop
quality.
The most notable of these crops are potato and tobacco.
A number of experiments have been conducted in which the effects
of KCl and potassium sulfate (KgSO^) on the quality of potato tubers
have been studied.
studies.
Potassium nitrate was included in some of these
These studies have shown in general, that the chloride source
of potassium as compared to the sulfate or nitrate source resulted in
a decrease in the specific gravity, dry matter and starch content of
the tubers.
These effects are generally associated with a reduction in
tuber quality.
As a result of the effects of chlorides on quality of
potatoes, in many of the commercial potato growing areas it is recom­
mended that the potassium be added as the sulfate.
However, when large
amounts of fertilizer are used and the potassium is supplied as the
6
sulfate and ordinary superphosphate is used, the quantity of sulfate
sulfur which is applied to the soil is in excess of that needed by the
plants.
While the effects of this excessive sulfate ion on the yield'
and quality of potato tubers has not been studied extensively, a tip
burn associated with high sulfate ion in the presence of ammonium
nitrogen has been reported (29).
McCants (29) further states that the effect of chlorine on the
quality of tobacco has been reported by many investigators.
The data
show that generally as the percentage of chlorine in tobacco is in­
creased, the green leaves frequently become thickened and brittle and
I
roll upward at the leaf margins.
When cured, the leaves are dull in
appearance and soggy, and associated with this condition is à reduction
in the duration of burn. This effect of chlorine on the burning
characteristic of tobacco is so pronounced that there are laws in many
states which regulate the maximum percentage of chlorine permissible in
fertilizers for tobacco.
Potassium, however, tends to improve leaf
burning characteristics and consequently relatively high rates are
generally used.
These conflicting demands have resulted in the use of
K2SO4 and potassium magnesium sulfates.
There are indications that
excessive sulfate addition to tobacco may be undesirable (29).
Potassium nitrate may also be desirable in greenhouse production
in that this type of fertilizer does not cause an accumulation of solu­
ble salts in the soils.
K. D. Jacob claims that because of its high concentration of
nutrients, low hygroscopic!ty, high solubility, and good storage
7
characteristics, KNO3 offers many advantages to the fertilizer manu­
facture (24).
The claims he makes for KNO3 are that it:
1.
mixes well with other materials simplifying processing
of granular and non-granular fertilizers,
2.
is chemically neutral and stable and therefore under­
goes little or no chemical change in mixtures and does
not contribute to loss of nitrogen during processing,
3. tends to reduce the hygroscopicity of mixtures, and
thus favors maintenance of good mechanical condition,
4.
is useful for the formulation of mixtures having either
a neutral or an alkaline effect on the soil reaction
as it is alkaline whereas KCl and K2SO4 are neutral,
and
5.
has a low salt index and therefore reduces danger of
seeding injury and plant burn.
Chlorine Demand
Elemental chlorine is a possible co-product for KNO3 when it is
manufactured from HNO3 and KCl.
Therefore, the status of CI2 as an
item of commerce is important.
In July, 1962, it was stated that during the prior six months the
demand for chlorine increased so sharply that processors were moving
fast to fill orders (20).
Expansions were in the works but the ques­
tion was: Will the expansions planned be enough? The production of
chlorine was then 4.9 million tons per year, which was 92% of capacity.
A total requirement for 1967 of 6.3 million tons was predicted.
It
was also reported that there had long been concern that over capacity
in caustic might accompany the chlorine growth.
However, industry
spokesmen expected caustic use of about 6.6 million tons by 1967 and
no serious overcapacity.
Reaction between Potassium Chloride and Nitric Acid
Mehring, Ross and Merz (30) have studied the reaction
3KC1 + 4HN03 = 3KN03 + Cl2 + N0C1 + 2H20
They found that under various conditions all of the KCl was converted
to KNO^.
However, the chlorine and some nitrogen were evolved as mix­
tures of hydrochloric acid (HC1) nitric acid (HNO3) chlorine, nitrosyl
chloride (NQC1) and water vapor.
They found these mixtures difficult
to separate.
Mirkin (32) also studied this reaction and found that it did not
go to completion.
He found yields on the basis of the nitrogen amountI
ed to 45% almost independently of the concentration of the acid used.
The yield based on the potassium fluctuated, depending on the strength
of the acid, from 60 to 75%.
The gases which were evolved were pri­
marily CI2 and N0C1.
Nikonova and Epshtein (19, 34) have calculated the free energy
change for standard conditions, starting with crystalline KCl and
liquid HNOg and ending with solid KNO3 and all other products as
gases, to be -5,563 cal/mole.
They have calculated the heat of re­
action to be 16,350 cal/mole under the same conditions.
Patented Processes
Kobe (27) describes a process shown in Figure 1 for the manufac­
ture of NaNOg and Cl2 which is used by the Solvay Process Company.
Salt is fed into a reaction tower which contains a solution having at
least 40% nitric acid at a temperature of 'about 60° C.
At this
temperature and concentration no hydrogen chloride is evolved.
The
solution from the reactor is withdrawn to a cooler where the tempera­
ture is reduced to 30° C. The NaNOj that crystallizes out is filtered
off and the filtrate returned to the reaction tower.
The HNO3 con­
centration is maintained by bubbling N02 into the reactor.
The gas
evolved from the reactor is mainly NCC1 which passes to a condenser
in which it is cooled to 0° C. to dry it.
is returned to the reactor.
The moisture condensed out
If the amount of moisture in the gas is
maintained below 0.1% the corrosion is greatly reduced.
The dried
NOC1 is mixed with oxygen in the ratio of 2 to 1 and the mixture is
passed into an oxidizer in which it is contacted at an elevated tempera­
ture with a catalyst.
This reaction is
2N0C1 + 02 = Cl2 + 2N02
An alternate method is to liquify the N0C1 and conduct the oxidation in
the liquid phase at 60° C. and 400 psi.
This process with many possible changes is covered by patents
issued to Beekhuis (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14).
These
patents describe the process as outlined above except that different
10
methods are used for oxidizing N0C1.
In some cases it is oxidized in
the liquid state at other times it is oxidized as a gas with air.
patent covers the oxidation of N0C1 with HNO3.
One
The reaction is
NOC1 + 2HN03 = 3N02 + 1/2C12 + HgO
In this case at least some of the N02 must be absorbed in water to
form HNO3 and the resulting NO must subsequently be oxidized and ab­
sorbed.
Some of Beekhuis's patents allow the use of HNO3 in place of
NO2 and the removal of water.'
Fogler claims that the process uses HNO3 rather than N02 (22).
In his diagram of the process no liquid is returned to the reaction
tower from the filter.
reactor.
Thus the reaction tower is a once through
However, he claims virtually complete conversion of NaCl.
A
mole ratio of about 1 to 1.7-1.9 NaCl to HNO3 is used (22). The vessels
for the reaction are constructed of acid-resistant brick and chromeiron alloys.
Miller (31) reports carrying out the following reaction in a
1
slurry
2NaCl + Mn02 + 4HN03 = 2NaN03 + Mn(N03)2 + Cl2 + 2H20
The chlorine is recovered from the overhead gases and the slurry is
cooled and filtered to remove the nitrates.
Following the filtration
the solution is returned to the reaction vessel and the iolid nitrates
are heated to above 200° C. and contacted with air to oxidize the man­
ganese nitrate.
2Mn(N03)2 • H20 + 02(air) = 2MnC;. + 4HN03
11
The acid is recovered by suitable means and the NaNOg is leached from
the manganese dioxide (toi02) with a hot solution from which it may be
recovered by cooling.
Mn02 is returned to the reaction vessel.
Miller also mentions that the Mn02 may be kept separate from the
reaction vessel and reacted with the N0C1 in the off gases as follows:
2N0C1 + 2Mn 0 2 = MnCl2 + Mn(NOg)2
It is then necessary to react the resulting MnCl2 with HNO3 and more
Mn02 as follows:
MnCl2 + Mn02 + 4HN03 = 2Mn (N03)2 + 2H20 + Cl2
The resulting Mn(N03)2 is treated as it was in the above case.
Stengel has been issued several patents covering a process for
the manufacture of KNO3 (43, 44, 45).
Two of the: e patents relate to
processes for separating HC1 and HNO3 while the other (44) relates to
1
a process for production of KNO3. In his process a bed of KCl is
maintained at a temperature above the melting point of KNO3, 333° C.
The vapors evolved by heating HNO3 are passed through the bed and the
KN03 formed melts and flows from the reactor. Since the KNO3 leaves
the surface of the KCl as it is formed the reaction is allowed to go to
completion rather than only partially as is usually the case in react­
ing solid KCl in the absence of water and the separation problem is
reduced.
Stengel preferred to use dilute nitric acid, less than 35%
by weight, because this reduced the output of noncondensable gases
such as the nitrogen oxides.
Two different processes for producing KNO3 using an organic
12
solvent have been patented (1, 28).
Baniel and Blumberg (1) use a
solvent mixture consisting of water, an organic solvent and the acid.
The solvent mixture is so constituted that the salts are insoluble in
it. The following is part of the first example given: "The reaction
liquor is a homogeneous solution composed of 77 ml of 60% by weight
aqueous HNO3 and 50 ml of water made up with isoamyl alcohol to 1000
ml.
The acidity of this solution is 1.ON calculated on its total
volume. This liquor is contacted in a countercurrent manner with 56
gm of finely ground solid KCl.
The conditions, in particular the rate
of flow of the liquor and the total time of contact, are so chosen that
virtually all the KCl is converted to KNO3 by one single passage of
the liquor.
The solid end product, therefore, consists of KNO3 of a
degree of purity of 98% or even higher.
The solvent may be treated in
one of several ways: (a) The solvent phase is mixed with one half
its volume of benzene. The water and acid content of the solvent
phase is separated as a bottom layer and can be drained off the solvent
mixture, (b) The solvent phase is extracted with aqueous chloride
brine whereby HNO3 is preferentially extracted."
Lovell (28) dissolved NOg in a halogenated hydrocarbon such as
carbon tetrachloride and then suspended KCl in the solution.
Water in
an amount equivalent to about 3% of the chloride increases the reaction
rate. However, at 20-28° C. only about 55% of the KCl is converted to
KNO3 in 90 minutes.
In four- hours 88.5% is converted.
made of possible recovery of the N0C1 released.
No mention is
13
Production of Potassium Nitrate at Vicksburg
The Southwest Potash Division of American Metal Climax began
production of fertilizer grade KNO3 in its Vicksburg, Mississippi
plant in the fall of 1963 (36).
Although the plant was completed in
the spring of 1962 a series of engineering difficulties delayed high
level production.
Company officials said the difficulties involved
equipment and corrosion in unexpected areas.
While the capacity of
the plant has not been released it is reported to have cost $7 million
(25) and alternatively $8 million (36).
Reportedly the plant is designed to turn out KNO3 and chlorine
(from KCl and dilute HNO3) (25).
However, until its patent position
is entirely settled, the company will divulge little information about
the process, nor will it reveal the capacity of the plant (36).
Analysis
E. L. Nelson presented a method for determining the total nitro­
gen in materials containing nitrate (33).
Wolf and Schier (49) have
developed a conventional analysis for mixtures of N0C1, NOg and CI2.
Details on these procedures are in Appendix A and Appendix B.
Gas Chromatography
Horton has had some success in separating the oxides of nitrogens
on a dry silica gel column, partly at ambient temperatures and partly
14
at elevated temperaturesHe claims to have also separated N0C1,
N20, and Cl2.
His results are at best semiquantitative.
Others have separated N2 and NO on silica gel columns both at
elevated and dry ice temperature (2, 39).
NO and N02 have been separated on Ballatine glass spheres (41).
The 0.02 mm spheres were cleaned with chromic acid, washed and then
heated to 300* C. for 3 hours.
The spheres were then placed in a
column 4 mm i.d. by 4 feet long and conditioned with NO and N02 for 2
days.
The separation was carried out at -25° C.
The products of the reaction
N02 + 2HC1 = NOCl + H20 +1/2 Cl2
have been separated by gas-liquid partition chromatography (46). The
separation was carried out at room temperature, using a 12 foot column
of Celite 545 and dimethyl phthalate (50% by weight) with hydrogen as
the carrier gas.
The column would not separate N02 from the products
of the above reaction so an excess of HC1 was used.
Isbelï separated various gases with a column containing 25%
1
triacetin on non-acid washed -30 + 60 mesh Chromosorb P (Fisher
Scientific Co.) (23).
tubing.
The column was 8 feet long by 5 mm i.d. copper
The helium carrier gas was supplied at 18 psi and 108 ml/min
measured at atmospheric pressure.
Some of the retention times he
found, in minutes, were C02, 0.54; Cl2, 0.80; (CN)2, 1.02; NO, 0.48
*A. D. Horton, Oak Ridge National Laboratory Oak Ridge, Tennessee.
Separation of the oxides and chlorides of nitrogen. Private communica­
tion. 1962.
15
I
and C>2» 0.48.
Runge separated various inorganic gases using a column packed
with Aroclor 1232 on Haloport F (37). The following table gives re­
tention times for various gases in a column 9 m by 6 mm i.d. filled
with Aroclor 1232 on Halaport F in ratio 1:20.
The carrier gas was
200 ml H2/min and the temperature was 22° C.
Table 1.
Retention time of various gases relative to air
Gas
Time, sec
Air.
CO
C02
HC1
0
0
12
36
HCN
(CN)2
CL2
C1CN
147
89
213
426
C0C12
N0C1
S0o
518
323
253
Unfortunately the N0C1 was dissolved in CCI4 which gave the long
retention time.
Solubility of KCl and KNO3 in Water
Figure 2 shows the individual solubilities of KCl and KNO3 in
water (40).
The KNO3 solubility is much more temperature dependent
I
16
than the KCl solubility.
These solubilities indicate the possibility
of a fractional crystallization process in which KNO3 is crystallized,
from a solution containing both KCl and KNO3, by cooling the solution.
I
I
I
&
Figure 1.
Solvay Process Company's sodium nitrate process (27)
Figure 2.
Solubilities of KNO3 and KCl in water (40)
18
Oxidizer
Liquefier
C'a
product
NaCl
feed
Separator
Condenser
Filtrate
rv
Liquid
Reaction
tower
Froctionotor
NOz+ NOCI
NaNO,
product
HI fMffttfff.
Filter
Cooler
280
240
KNO,
200
Solubility,
gm/IOO gm, 60
water
120
80
KCl
40
0
10° 20° 30" 40° 50° 60* 70° 80° 90° 100'
Temperature, e C
19
GAS CHROMATOGRAPHY
Introduction
Any reaction to produce KNO3 from KCl will probably form volatile
compounds.
A chromatographic analysis of these gases seemed to be the
most desirable.
Among these compounds there might be HC1, Cl2, NO, NOCI.
Also air might be mixed with the gas from the reaction.
attempt was made to separate all of these compounds.
Initially an
Later as the
nature of the process was better defined and the gases actually present
identified by wet methods of, analysis many of these compounds were
eliminated.
In the final analysis it was only necessary to separate
NOCI, CI2 and air.
The development of a suitable chromatographic
method for this separation is described below.
Gas-Solid Chromatography
I
Silica gel
The column was prepared by filling a 1/4 in. o.d., 20 BWG 304
stainless steel tube 1.5 meters long with analytical grade silica gel.
A particle size range of -20 + 35 mesh (U. 5. Standard) was used.
The
column was then dried by heating at 275° for 2 hours.
Samples of NOCI and N02 were injected into the column when %t was
at 60, 80 and 100° C. and the carrier gas flow rate was constant at
30 ml. He/min.
No peaks were observed for either of these gases under
20
these conditions.
However, at the same flow rate but a column
temperature slightly higher than ambient, a NO] sample showed a peak
very close behind the air peak.
At 35° C. peaks for both NO] and NOC1
were observed which were superimposed upon one another and overlapped
the air peak.
At 40° C. the air peak and the NO2-NOCI peak were
farther apart but the NO2-NOCI peak had become quite low and flat.
It
was further observed at 40° C. that the NO] or N0C1 peaks became pro­
gressively lower and flatter when one sample after another was injected
into the column.
This was true even if the time between sample in­
jections was increased to 20 min. and indicated that some gas from
early injections may have been retained in the column, giving a poor
analysis.
Glass beads
Minnesota Mining and Manufacturing Company's "Superbrite" glass
beads (-200 + 325 mesh) were used to pack a column consisting of 10 ft.
of 1/8 in. o.d., 20 BIVG stainless steel tubing.
Before being placed in
the tubing the beads were washed in chromic acid and aqua regia and
then dried.
Helium at 40 psig was used as the carrier gas.
At gas flow rates
of 11, 4.5 and 3.0 ml/min and -78° C., NO2 did not show a separate peak
from air.
Since the melting point of NO2 is -9.3° C. it may have been
retained in the column.
At -25° C. and 7.0 ml He/min flow rate neither
NO2 nor CI2 produced peaks which were distinct from the air peak.
At
room temperature and 6.0 ml He/min the introduction of a NO] sample did
21
not produce a peak separate from the air neak.
Molecular sieves
A column was prepared from 7 ft. of 1/4 in. o.d., 20 BWG 304 stain­
less steel tubing and was packed with type 5A molecular sieves (-30 +
1
60 mesh). The column separated air at room temperature and a flow rate
of 30 ml He/min. The Og came out at 6.5 min and the Ng at 14 min.
When CI] was injected with air only the two original peaks showed up as
was the case when linear temperature programming to 300° C. was
employed.
At room temperature and a flow rate of 45 ml He/min the O2 peak
I
was at 4.6 min and the N2 peak was at 11 min.
When N0C1 and NO2 were
individually injected into the column only a slight peak at 11 min was
observed.
This peak was probajbly due to air in the samples but in any
case would not give a separation of these gases.
Alumina
An 8 meter by 1/4 in. o.d., 20 BWG copper tube was packed with
F-20 Alcoa activated alumina (-20 + 100 mesh).
At a flow rate of 30 ml
He/min and room temperature air showed a peak in 6 min.
peak appeared at 7 min but CI2 did not show a peak.
A good N0C1
Apparently CI2
(
was irreversibly absorbed.
I
When the flow rate was reduced to 20 ml He/min and the tempera­
ture increased to 50° C. the air peak appeared at 6.5 min and the
22
N0C1 peak at 7.1 min.
Again no peak was observed when CI2 was in­
jected into the column.
Gas Liquid Partition Chromatography
Aroclor 1232 on Halaport F
A 20 ft. by 1/4 in. o.d., 20 BWG stainless steel tube was packed
with 1 part Aroclor 1232 on 20 parts Haloport F.
At 27° C. and a
flow rate of 195 ml He/min, air came out in a single peak at 1.2
min and NOC1, NO] and Cl2 all came out in 1.4 min.
At 22° C. and a
f
flow rate of 115 ml He/min, air, N0C1, NO] and CI] all came through
the column in 1.1 min.
The use of H2 as the carrier gas did not im­
prove the results.
1, 2, 3 tris (2-cyanoethoxy) propane on Chromosorb P
A stainless steel tube 6 ft by 1/4 in. o.d., 20 BWG was packed
with 40 gm of 1, 2, 3 tris (2-cyanoethoxy) propane on 100 gm of
acid washed Chromosorb P.
At room temperature and 85 ml He/min, NO],
Cl2 and air all came through the column in 0.3 min.
At 40 0 C. and
25 ml He/min, NO] and air still came out in a single peak at about
0.8 min, but chlorine appeared as a separate peak at about 1.1 min.
The peak tailed badly, however, and in general was low and misshapen.
Dimethyl phthalate on Chromosorb W
Non-acid washed Chromosorb W was screened and the portion passing
a 30 mesh screen and retained on a 60 mesh screen was used.
This
23
inaterial was coated with 50 gm of dimethyl phthate per 100 gm solid
and was used to pack a 12 ft by 1/4 in. o.d., 20 BWG copper tube.
At room temperature and a flow rate of 30 ml He/min, air, CI] and
N0C1 all came through the column in 1.3 min.
At the same flow rate
but at 75° C. these same gases gave a single peak at 1.2 min.
Similar
results were experienced at 50° C., 35° C. and room temperature with
a flow rate of 92 ml He/min.
Triacetin on non-acid washed Chromosorb P
Non-acid washed Chromosorb P was coated with 25 gm triacetin per
100 gm Chromosorb and used to pack an 8 ft by 1/4 in. o.d., 20 BWG
steel tube.
This column was found to give separate peaks and was
deemed satisfactory even though the N0C1 peak led considerably.
best separation was observed at 75° C. and 100 ml He/min.
The
The N0C1
peak was better if the column was loaded with 5 ml NO] about 30 min
before the analysis.
Figure 3 shows the peaks obtained when 400 ml of gas from the
continuous reactor (containing air, CI] and N0C1), was injected into
the column.
The air peak was attenuated to 1/4 of its relative size to
insure that it did not go off scale.
Calibration plots were made showing volume of sample versus peak
area.
Figures 4, 5 and 6 show the calibrations used in the analyses
made on the gases evolved during the continuous reactor runs.
Figure 3.
Chromatographic analysis of reaction product gases using
triacetin on non-acid washed Chromosorb P
DEFLECTION, PERCENT OF FULL SCALE
K)
cn
m
3
3
Figure 4.
Peak area versus volume of air
Figure 5.
Peak area versus volume of NOCI
27
28
26
20
S12
Flowrofe : 100 ml He/min
Temperature: 75° C
20 40 60 80 100 120 140 160 180
AIR SAMPLE SIZE, ft\
FLOW RATE: 100 ml He /min
TEMPERATURE: 75°C
I
40
80
120
ISO
200 . 240
NOCI SAMPLE SIZE,/il
280
320
360
400
Figure 6. Peak area versus Cl] volume
140
130
120
TEMPERATURE: 75
MO
100
90
80
< 70
w
< 60
« 50
UJ
40
20
10
0
40
80
160
200
Cl 2 SAMPLE SIZE p. I
120
240
280
300
30
BATCH STUDIES
Equipment and Procedures
Figure 7 is a schematic drawing of the equipment.
A 500 ml round
bottom flask was used as the reactor and was fitted with a condenser
and a vessel for adding the acid.
The condenser in turn was connected
to a series of absorbers fitted with fritted glass bubblers.
Solid
KC1 was placed in the reactor and the reaction and absorption system
was swept out with nitrogen gas.
Then the acid was added to the re­
actor from the vessel and the reactor was kept in a constant tempera­
ture bath or heated with a flame.
Normally the first two absorbers
were charged with 96.7% sulfuric acid and the last one with a 10%
solution of potassium iodide.
In the first two absorbers NOCI was expected to react to form
NOHSQ4 and HCI while the CI2 was expected to react in the third ab­
sorber to form KC1 and free iodine.
Following the reaction the system
wals again swept out with nitrogen gas in order to pass any residual
NOCI and CI2 gas into the absorbers.
In some of the runs the first absorber was used as an oxidizer
to oxidize the NOCI to CI] and nitrogen oxides.
Nitric acid or man­
ganese dioxide in hot nitric acid was used as the oxidizing agent.
Following the reaction the residue in the reactor was analyzed
for NOg- and Cl~ ions. The HC1 which should have been formed in the
first absorber by the reaction of NOCI with H2SO4 was not found there.
Figure 7.
Batch reaction equipment
ACID CHARGE
i
VESSEL
CONDENSER
WATER
OJ
M
REACTOR
SOLID KCI
t—i
1—J
ABSORBERS
33
Therefore, the H2SO4 in the second absorber was replaced with water for
one of the runs. The HCl was then absorbed in the water.
Analytical Procedures
The chloride was determined by the gravimetric method for silver
chloride.
This was done by adding a solution of 0.25M silver nitrate
to a solution of the material to be analyzed.
Subsequently the pre­
cipitate of silver chloride was filtered, dried and weighed.
The nitrogen analysis was made by the method of Nelson (33).
This method is described in Appendix A.
The method of Wolf and Schier (49), described in Appendix B, was
used to analyze the products of the reactions between the gases and
the various materials in the absorbers.
The KI solution was analyzed
for free iodine, using sodium thiosulfate.
I
Results and Discussion
The data which were taken in the batch studies can be divided into
two groups.
One segment of the information consists of the data which
were taken when there was an attempt in the first absorber to oxidize
the nitrosyl chloride to free chlorine and other nitrogen products.
The other part consists of those data that were taken when no attempt
was made to alter the gases. Runs I, III, VI, VII and VIII involved no attempt to oxidize the
34
nitrosyl chloride.
Table 2 gives the material balances for these runs.
During Run I the reactor was maintained in a constant temperature bath
at 55° C; during the remainder of these runs at 72 to 74° C,
The gases
were bubbled through two sulfuric acid absorbers and then into a
solution of 10% potassium iodide in water.
I
Table 2.
Material balances for initial runs
Run temp, °C
Item, moles
I
55
III
73
NOj
CI"
.NO"
Cl-
Used
0.0390
0.296
0.390
0.315
Residue
0.306
0.2152
0.360
0.2118
H2S04 absorber
0.0122
0.0128*
0.0333
0.0327*
Total N
(0.0122)
(0.0333)
NO
(0.0128)
(0.0327)
KI absorber
0.0160
Total
0.3182
0.2440
Percent
accounted for
81.85
82.50
0.0646
0.3933
100.8
0.3091
98.2
*Credit due to NOHSO4 analysis, not actual CI" analysis.
35
Table 2. (Umiinued)
VI
73
VII
73
VIII
73
Run temp, °C
Item, moles
NO-3
CI"
NO",
CI"
N0"3
CI"
Used
0.388
0.296
0.388
0.302
0.388
0.300
Residue
0.360
0.187
(0.3555) (0.2023) (0.3381) (0.1773)
Solid
0.1765
0.0668
0.2054
0.0511
Solution
0.1770
0.1355
0.1327
0.1262
0.0308
0.0302* 0.0370
0.0338
H2S04 absorber
0.0306*
Total N
(0.0338)
(0.0308)
(0.0370)
NO
(0.0306)
(0.0302)
(0.0382)
0.0576
KI absorber
0.0536
0.0672
HgO absorber
0.0356
Total
0.3838
0.2752
0.3843
0.2861
0.3751
0.2801
Percent
accounted for
99.00.
93.00
99.15
94.80
96.70
93.50
The analyses were carried out as described above.
From the
results of Runs VII and VIII it can be seen that the solid residue
was 20-25% KCI.
chloride.
This would naturally be an unacceptable level of
Also from these material balances one can see that very
little HCI or HNO3 was evaporated from the reactor and that the ex­
pected reaction,
4HN03 + 3KC1 = NOCI + Cl2
did occur.
KCI.
+ 3KN03 + 2H20
Runs were made with 4 moles of HNO3 for every 3 moles of
36
Following the above experiments several were made in which the
flask was heated with a flame and the solution was evaporated to dry­
ness.
It was hoped that by this method a product which was 100% KNO3
could be produced.
Table 3 shows the compositions of the products of
these runs.
Table 3.
Composition of material remaining in the flask after
evaporating nearly to dryness
Run
NO3™,
moles
Cl~, moles
CI", mole %
IX
0.2822
0.106
3.6
XI
0.2705
0.0615
18.5
XII
0.300
0.056
15.7
XIII
0.292
0.0367
11.2
XIV
0.285
0.0284
9.1
XV
0.3122
0.029.
8.5
XVII
1.159
0.136
10.5
The data in Table 3 show that the residues of mixtures containing
4 moles of 60% HNO3 for each 3 moles of KCI contained excessive amounts
of chloride ion.
While the amount was not constant, it was in all
cases too high to be acceptable.
Runs IX and XVII were also used to study the effectiveness of
oxidizing NOCI with HNO3 or Mn02 in HNO3.
The reactions which were
expected to occur when hot 70% HNO3 or MnO] in 70% HNO3 was placed
37
in the first absorber are
NOCI + 2HN03 = 1/2 Cl2 + H20 + 3N0
2N0C1 + 2MnÛ2 = MhClg + Mn(N03)2
MnCl2 + Mn02 + 4HN03 = 2Mn(N03)2 + 2HgO + Cl2
From Table 4 it can be seen that these reactions did occur to a
significant extent.
Table 4.
Run
Effectiveness of oxidizing NOCI with HN03 or Mn02 in HN03
Oxidizing
treatment
Portion of chloride evaporated
from reactor which was found
as free chlorine, percent
IX
none
65.2
XI
none
77.0
XII
Mn02 in HNO
96.5
XIII
Mn02 in HN03
91.5
XIV
HN03
92.6
XV
HN03
108.0
XVII
none
70.04
38
SOLUBILITY STUDIES
Technique
Laboratory
Aqueous HNO3 solutions containing both KCI and KNO3 and extending
in concentration over the range of interest were added individually to
an excess of both solid salts.
constant temperature bath.
These mixtures were then placed in a
At equilibrium three phases were present
which consisted of a solid phase for each of the two salts and an
aqueous solution.
After the system reached equilibrium part of the
aqueous phase was decanted, weighed, placed in a volumetric flask and
made up to volume in preparation for analysis.
Solubility was studied
at 0, 16, 30, 45 and 60° C.
..
1
Also aqueous solutions containing 0.304 gm of HNOj/gm water were
added to excess amounts of KNO3 and controlled amounts of KCI.
These
mixtures we're allowed to come to equilibrium in a constant temperature
bath at 30° C. At equilibrium two phases were present, solid KNO3 and
an aqueous solution.
Part of the solution was decanted, weighed and
made up to volume with distilled water in a volumetric flask in
preparation for analysis.
Analytical
Potassium was determined by a flame photometer using a propane
flame and lithium as an internal standard.
Chloride was found by the
39
silver chloride method.
method.
Nitrate was found by the standard Kjeldahl
The acid content was found by titration with NaQH.
Results and Discussion
Mutual solubility of KCI and KNO3
Several figures were plotted to show the mutual solubilities of
KCI and KNO3 i-n aqueous solutions of nitric acid and various acid-water
ratios and temperatures.
Figure 8 shows the solubilities at 0°C of KNO3 and KCI in aqueous
nitric acid solutions in contact with both KCI and KN03 solid phases.
The curve reaches a minimum at about 0.31 gm HN03/gm HgO.
The value
at this point is -Ô.312 gm KNC^/gm solvent or gm KN03/gm (H2O + HN03).
Where the solubility is negative KCI has gone into solution and KNO3
has salted out with the K+ coming from the KCI in solution and the NO3coming from the nitric acid.
Figures 9, 10, 11 and 12 show the mutual solubility curves for
KNO3
and KCI solutions in contact with both KCI and KNO3 at 16, 30, 45
and 60° C.
The KNO3 solubility curves for 0, 16, and 30° all have two
relative minimums.
The lower of the two minimums at 30° C occurs at
about 0.30 gm HNO3/gm H2O.
gm KNÛ3/gm (H2O + HNO3).
The solubility at this minimum is -0.195
The KNO3 solubility curves for 60 and 45° C
have only one minimum each.
Figures 8, 9, 10, 11 and 12 also show the mutual solubility of
KCI in solutions at 0, 16, 30, 45 and 60° C.
These solutions are in
40
contact with solid KCI and KNO3.
maximum and minimum.
Each KCI solubility curve shows a
It can be observed that none of these curves
extends into the negative region.
In general the solubility of both salts increases as the
temperature increases, although this is not quite true for all of the
curves. The KCI solubility does not respond very readily to tempera­
ture.
Intuitively this would seem proper as in water the solubility
of KCI does not increase with temperature nearly as much as does the
solubility of KNO3.
It was thought that the KNO3 curves should be similar at various
temperatures.
Therefore they were drawn as a series, i.e., the curves
at 0, 16, 30° C were drawn in much the same manner even through the
16° C curve may have been drawn differently if no other data were
taken.
Also the KCI curves were drawn as a series.
If only the data
for 30° C were available this curve might have been drawn as a
straight line.
At 0, 16 and 30° C the KNO3 solubility decreases rapidly from
the value it has in water as the HNO3/H2O ratio is increased.
due to a common ion effect.
This is
However, at about 0.3 gm HNO3/8™ ^0 it
reaches a low point and then increases rapidly.
That the low points
on the figures are the same as the actual low solubility point is
doubtful for it would be fortuitous if the acid water ratio with the
lowest KNO3 solubility had been chosen.
However, there is little doubt
that a rather abrupt minimum occurs. The KCI solubility does not
41
decrease very rapidly as IINO3 is added to the solution until a ratio
of about 0.3 gm HNOg/gm H20 is reached, or about the minimum KNO3
solubility point.
Then as the KNO3 solubility increases rapidly the
KCI solubility decreases rapidly. The KCI solubility experiences a
minimum at the same place that KNO3 solubility experiences a relative
maximum, 0.8 gm HNO3/gm H20.
At 45 and 60° C much the same thing
occurs at about 0.5 gm HNO3/gm HgO but to a lesser extent.
Apparently
there is a fundamental change in the nitric acid-water system at a
concentration of about 0.3 gm HN03/gm H^O at 0, 16, and 30° C with
the same change occuring at a higher acid concentration at 45 and 60°
C.
More data were taken at 30° C than at the other temperatures as
this is a temperature which can be reasonably reached with cooling
water and therefore is of more interest.
In order to separate KNO3 from KCI by a fractional crystallization
process one needs a low KNO3 solubility and a high KCI solubility at
a reasonable temperature such as the 30° C temperature previously pro­
posed.
Upon examining the 30° C solubility curves for the two salts
one can see that at an acid to water ratio of about 0.30 the solubility
of KNO3 is at its lowest value, -0.20 gm/gm (HgO + HNO3) while the KCI
solubility is high, about 0.30 gm/gm^H^O + HNO3).
Therefore it would
seem from solubility alone, ignoring other process requirements, best
to crystallize KNO3 from a solution containing about 0.30 gm of acid
per gm of water.
42
Solubility of KNO3 in solutions not saturated in KCI
It was desirable to know how much KNO3 might be crystallized upon
cooling to 30° C any given solution containing 0.30 gm HNO3/ gm H2O
and various amounts of KCI and KNO3.
Therefore data were taken to
determine the solubility curve shown in Figure 13.
Point A is the
mutual solubility point of KCI and KNO3 in a solution containing 0.304
gm HNO3/ gm HgO.
KCI and KNO3.
The solution is in contact with two solid phases,
All other points on the curve represent solutions which
are saturated with KNO3 but not with KCI.
Above the curve is the un­
saturated region and below it is the two phase region.
In the following section is a discussion of how much KNO3 could be
crystallized by cooling reactor samples to 30° C. None of the typical
samples taken would have become saturated in KCI by cooling to 30° C.
Figure 8.
Mutual solubility of KNO, and KCI at 0°
I
Figure 9.
Mutual solubility of KN03 and KCI at 16°
44
0.300
io
0
z
1
+
°cu
0.200
0.100
I
E
o»
•s
0.000
ÎJ
<
V)
I -o.ioo
-0.200-
— 0.300 —
0.00
1.00
2.00
gm HNO^/gm H^O
0.400
0.300
0.200
E
01
0.100
<
o
0.000
-0.100
-0.200
-0.300
1.00
gm HNOg/gm HgO
2.00
Figure 10.
Mutual solubility of KN03 and
KCl at 30 C
Figure 11.
Mutual solubility of KNO3 and KCl
at 45° C
0700
0600-
0.500 —
0.400
10
o
2
X
+
E
o>
0.300
Q200I—
CT>
N
h
g
E
o»
KNOjj
0.100
o
-0.100
-0.200 -
100
qmHNOj/gm HgO
ZOO
2.80
-0300
1.00
gm HN0j/gmH^0
2.00
2.80
Figure 12.
Mutual solubility of KNO3 and KCl at 60° C
Figure 13.
Solubility of KNO3 at 30° C in solutions of 0.304
gm HNO3/gm HgO containing various amounts of KCl
48
0.700
0300
0.401
x 0300
KCL
0.100
KNO
0.00
-0100
-0300
1.00
2.80
2.00
KCl, Percent
.100
Unsaturated
Region
••36
i96
•32
\92
,88
-28
-24
<84
Solvent
(H20*HN03)
Percent
KNO;, Percent
-16'
30° C
V
0.304gm HN0 3 /gm H 2 0 V*
16
20
KNO,, Percent
28
49
CONTINUOUS RUNS
Runs without Supernatant Liquid Return
Equipment
Figure 14 is a schematic drawing of the equipment.
The reactor
was a three-necked, 1000 ml flask with a 600-watt heating mantle and
a powerstat for temperature control.
The reactor was fitted with
equipment to withdraw the liquid, remove the gas formed, add solid
KCl and nitric acid solution, and measure the temperature.
Ejectors
were used to maintain the vacuum.
The liquid was withdrawn through a fritted glass tube and
collected in a 250 ml graduated cylinder.
A heating tape was used
to heat the liquid draw line to prevent precipitation of KNO3.
The gas passed through a condenser to remove the water and any
acid in the vapor, and the condensate was collected in a second 250
ml graduated cylinder.
The temperature in the reactor was sensed
with a copper-constantan thermocouple and recorded with a millivolt
•v.
meter strip chart recorder.
An opening in the vapor line was connected
to a mercury manometer for pressure measurement.
Procedure and difficulties
The following procedure was used in the first runs with this
equipment: 1.
The acid feed rate was arbitrarily fixed and from this,
the KCl feed rate was determined as 3/4 as great mole per mole.
2.
The
pressure was arbitrarily set using the ejectors.
3.
The liquid was
withdrawn at a rate such that the potassium inlet and exit rates were
equal.
Additional water was added to replace the water which was removed
in the draw.
4.
The powerstat and thereby the vaporization rate was
set so that the water removed as vapor equaled the water added and
produced by reaction.
5.
The liquid and solid products from the liquid
receiver were analyzed for H+, K+, NO^ and Cl~ ions.
Two semi-continuous runs were made with the 1000 ml reactor using
60% by weight HNO3 and dry KCl as feed stock.
arose in feeding the KCl.
Several difficulties
Also the liquid draw line frequently became
plugged due to the fact that KNO3 crystallized from the nearly saturated
solution upon only slight cooling.
These difficulties shut down these
runs before any significant data could be taken.
Subsequent to these runs it was decided to use 30% by weight nitric
acid in order to minimize the difficulty encountered in withdrawing the
liquid from the reactor.
After this change it was possible to operate
the equipment although the feeding problem still remained.
Runs C, D
and E were carried out usin-g 30% by weight HNO3 feed.
Results and discussion
Figures 15, 16 and 17 give the concentrations in the reactor of
NO™, Cl~, and H+ in moles per liter for runs C. D and E.
runs 30% by weight HNO3 was fed to the reactor.
In each of these runs
the reactor temperature varied from about 95 to 100° C.
was maintained between 660 and 710 mm Hg.
During these
The pressure
The reaction was started
Figure 14.
Continuous tests apparatus as initially constructed
52
NON-CONOENSABLES
BURETTE
KCl
CONDENSER
KC
WATER
\/
» ! VACUUM
CONDENSATE
RECEIVER
HEATER
i
i
REACTOR
LIQUID
RECEIVER
Figure 15.
Draw composition for Run C with solid KCl and 30% HNO3
fed, reactor at 100° C.
Figure 16.
Draw composition for Run D with solid KCl and 30% HNO3
fed, reactor at 100° C.
1
Figure 17.
Draw composition for Run E with solid KCl and 30% HNO3
fed, reactor at 100° C.
54
Concenîrofion,
moles/liter
3.0
30
• 60
120
90
Time in minutes
NO:
cr
40
80
120
160
Time in minutes
Concentration,
moles/liter
Time In minutes
200
55
with reaction products equivalent to 3/2 moles of KNO, formed in the
vessel.
Materials were added and withdrawn during each run at a rate
of 3/2 moles of KNO- formed per hour with an additional amount of water
being added to compensate for the water withdrawn to the graduate
cylinder.
Considerable effort was expended to assure that these runs
were the same.
Nevertheless, one can see from the figures that the
concentrations in the reactor were different for the different runs.
Further one can see that the ratio of NOj to CI" did not increase
much from the initial value of 4:3.
This means that the reaction,
HN03 + 3HC1 = N0C1 + 2H20 + Cl2
did not proceed as rapidly as desired at these concentrations.
Also
the figures show that there was considerable variation in the com­
position of the reactor solution between the three runs.
This indi­
cated that an approximation to a continuous process using the apparatus
and procedure described was extremely difficult to attain and that a
modified approach seemed advisable.
During these runs it was found that the material which crystallized
from the liquid which was withdrawn from the reactor was pure KNO3.
Runs with Crystallizer
Equipment and procedure
As a result of experience gained in the initial runs two changes
were made in the equipment.
The cylinder to which the reactor liquid
56
had previously been withdrawn was replaced with a three-necked 1000 ml
flask cooled by a water bath.
The flask contained a sintered glass
filter from which a valved line was installed to the top of the solid
feed vessel.
A reflux condenser was added to the vapor line just
above the reactor.
The equipment so modified is shown in Figure 18. ,
Following these modifications the procedure was changed to the
following:
1.
An initial charge of 4 moles of acid per 3 moles of
KCl was placed in the reaction flask.
2.
The ejector was turned on
and the pressure in the reactor was established at the desired value.
3.
Water was allowed to flow slowly through the reflux condenser and
at the normal rate through the final condenser.
was turned on.
5.
4.
The reactor heater
Acid and KCl were added in the proper ratio.
acid was fed from a burette through the solid feed vessel.
The
The KCl
was .charged to the feed vessel every 15 minutes and swept into the re­
actor by the acid feed and the returning supernatant liquid.
6.
Liquid
was withdrawn to the crystallizer from the reactor by opening the valve
in the vacuum line to the crystallizer and at the same time opening
the valve between the reactor and the crystallizer.
7. The liquid in
the crystallizer was cooled to 30° C. to produce a crystal crop of
KN03.
8.
By reducing the vacuum in the crystallizer and opening the
valve in the line to the solid feed vessel, the mother liquor was
transferred to the solid feed vessel and on into the reactor.
9.
Fol­
lowing the completion of the run the crystals were washed with an equal
volume of water.
The rate of heat input to the reactor was used to control the rate
Figure 18.
Apparatus used for continuous tests with crystallizer and reflux condenser added
60%_ HNO
Non-condensables
Vacuum
Solid KCl
1
r >1
/
Reflux
Cond.
Final
Cond.
H 2 0—
< y
Solid feed
Vessel
X
_^JocUUm
HgO^
T
Sintered
Gloss
Filter
i
Condensate
Receiver
Cooling H?Q Bath
Reactor
Cryslollizer
59
of water removal as vapor from the reactor in such a manner as to avoid
water build up or depletion in the reactor.
The rate of solution trans­
fer to the crystallizer was controlled so as to avoid a large build up
of solids in the reactor.
Results and discussion
Table 5 shows the results of Run 8.
The acid was fed at the rate
of 2 moles of F1NO3 as 60% solution per hour and the solid KCl at a
rate of 1.5 moles/hr.
Initially the reactor was charged (1) with 60%
solution containing 6.0 moles of HNO3 and (2) 4.5 moles of KCl.
The
run lasted 2 hrs and the average reactor pressure was 63 cm Hg absolute.
Table 5 shows the distribution of materials which were fed to the
reactor.
Only a small amount of HNO- showed up in the condensate be­
cause only a small amount (100 ml) was collected.
In order to keep
water from building up in the reactor more condensate should have been
collected.
The ratio, Cl"/H+ was nearly the same in the supernatant liquid
as it was in the crystals, i.e., 0.67. This indicates that the chloride
reported as being in the crystals was actually in the supernatant liquid
which was adhering to the crystals and not present as solid KCl.
If
it had been solid KCl the ratio of CI" to H+ would have been higher in
the crystals than in the supernatant liquid.
The residue which shows up in the reactor is of little concern
because in longer runs the amount of this material would be small when
compared to the total processed.
60
Table 5.
Material balance for continuous Run 8
Item
CI"
Amount, moles
H+
NO3
K+
Condensate
0.0984
0,129
0.224
0.0036
Supernatant from
crystals
0,268
0.236
0.403
0.101
0.665
Crystals
0.776
4.43
1.14
4.06
0.681
Reactor residue
1.95
3.54
2.19
3.30
Total
accounted for 3.095
8.33
3.96
7.47
Total added
7.50
10.0
10.0
7.50
Percent
recovered
41.3
83.3
39.6
99.6
Ratio, moles/mole
Cl"/H+
By examining Table 5 one can see the recovery of CI", and H+ in
the liquid and solid products was low, about 40%.
80% recovered in the liquid and solid products.
The N03 was about
The low recovery of
these materials was due to the fact that they react to form NOCl and
CI2 gas.
The recovery of CI" and H+ was low for all runs.
If the
recovery of these materials were high it would indicate the reaction
was not proceeding satisfactorily.
Table 6 shows the results of Run 9. The acid was fed at the rate
of 2.0 moles of HNO3 as 60% solution per hour and solid KCl at the
rate of 1.5 moles/hr.
Initially the reactor was charged with 6.0
moles HNO3 as 60% solution and 4.5 moles of solid KCl.
The run lasted
61
Table 6.
Material balance for continuous Run 9
I
Ratio, moles/mole
Amount, moles
Item
CI"
NOg
H+
K+
Condensate
2.03
0.883
2.87
0.0501
Cl~/H+
I
Wash of
crystals
0.391
1.40
0.667
1.12
0.586
Supemate from
crystals
0.167
0.205
0.287
0.0858
0.582
Crystals
0.006
5.131
-
5.19
Reactor
residue
0.334
2.50
1.93
0.901
Total
accounted for
2.93
10.1
5.76
7.35 '
Total added
7.51
12.2
12.2
7.51
Percent
recovered
39.0
82.1
47.2
97.9
1 hr and 10 min and the average reactor pressure was 52 cm Hg absolute.
Table 6 shows distribution of the materials which were fed to
the reactor.
Run 8.
The amount of condensate collected was larger than in
In this run 27.0% of the chloride, 10.6% of the nitrate and
22.4% of the acid appeared in the condensate.
This illustrated the
need for a counter current contacting device, such as a packed column
between the reactor and the reflux condenser.
Again in Run 9 no KCl was crystallized.
The ratio Cl"/H+ was the
same for the wash water as it was for the supernatant liquid,
indicating no solid KCl was dissolved by the wash water.
The water which was used to wash the.crystals contained about
25% of the KNO3 which was crystallized.
This showed that the wash
water will have to be returned to the reactor and the need for a
centrifuge or some similar device for separating the KNO3 crystals
from the mother liquor and reducing the volume of wash water required.
Runs with Final Equipment Modifications
Equipment and procedures
One of the important final equipment modifications was the
addition of a packed column, 2 1/2 in. o.d. by 18 in. long and packed
with 1/2 in. Berl saddles, between the reactor and the reflux con­
denser.
This column was added to the equipment to reduce the acid
loss to the condensate from the final condenser.
In a second change
the solid feed vessel was replaced with a 100 ml burette.
Finally,
a rotameter was placed in the vacuum line to measure the flow of noncondensables.
It was equipped with a Fischer and Porter precision
bore flowrater tube FP-1/4-16-5/36 with a glass float, 1/4-C. D.
The equipment with these modifications is shown in Figure 19.
The operating procedure was quite similar to that used previously.
Some improvements were made possible by the equipment modifications.
The condensate from the reflux condenser passed through the packed
column, counter current to the gases evolved from the reactor.
column effluent then returned to the reactor.
The
The KCl was added from
1
Figure 19.
Continuous test apparatus with final modifications
VACUUM
KCl
SOLUTION
60%». HNO
ROTAMETER
REFLUX
COND.
NON-CONDENSABLES
PACKED
COLUMN
FINAL
COND.
VACUUM
V
UKJ
SINTERED
GLASS
FILTER
i
CONDENSATE
RECEIVER
COOLING HgO BATH
REACTOR
CRYSTALLIZER
65
the burette an aqueous solution with a concentration of 27.9 gm KCl/100
ml of solution.
This allowed a steadier feed rate.
Measurement of the non-condensable gas flow rate in conjunction
with the gas analysis allowed the reaction rate to be determined.
Analysis of the various liquid products was carried out ais described
earlier.
The gas was sampled periodically and analyzed a.s described
in the section on gas chromatography.
Results and discussion
Table 7 shows the results of Run 0-2, the duration o:f which was
3 hrs and 15 min.
Four moles of HNO3 as a 60% solution amd 5 moles of
solid KCl were initially charged to the reactor.
The reactor was fed
2.0 moles of acid and 1.5 moles of KCl per hour.
Although the packed
column had not yet been added and the rotameter was improperly installed
this run is included in this section because KCl was fed as a solution.
The run demonstrated the improvement resulting from the moore uniform
KCl feed rate.
During the run, four samples were taken from the reactor, the
analyses for which are shown in Table 7.
The samples were removed by
attaching the existing draw line and a vacuum line to a sample bottle
and opening the valve in the draw line.
These samples represented
typical material which might have been transferred to the crystallizer
during the run.
In Run 0-2 about 20% of the chloride which was fed to the reactor
as KCl was found in the condensate.
The acid content (HNQg, KCl, etc.)
66
Table 7.
Material balance for Run 0-2
Cl-
Amount, moles
NO,"
H+
K+
.Condensate
1.575
0.895
4.03
——
Supernate from
crystals
0.894
0.558
1.10
0.340
Crystals
0.207
2.57
0.391
2.37
Reactor residue
0.313
3.69
0.398
3.61
Sample I
0.0676
0.272
0.0789
0.262
Sample II
0.0585
0.258
0.0772
0.236
Sample III
0.111
0.385
0.1450
0.364
Sample IV
0.0991
0.408
0.1488
0.366
Total accounted for
3.42
9.00
6.37
7.55
Total added
7.88
10.5
10.5
7.88
Percent recovered
43.4
95.0
60.6
95.9
Item
was also high.
From the analyses the amounts of HNO3, KCl and KNO3 in the
reactor were determined.
The ratio of gm HNO3/H2O gm was calculated
for each sample withdrawn from the reactor.
In each case the ratio
was found to be between 0.3 and 0.4 and therefore near the value used
in establishing Figure 13.
Therefore, Figure 13 can be used as the
solubility curve for these solutions at 30° C.
A line from the KN03
vertex of the triangular plot, and the point given by the fraction KCl
67
and fraction KN63 was urawn.
The final composition of the solution
upon cooling to 30° C. was given by the intersection of the line drawn
through these two points with the solubility curve.
Sample composition
along with the amount of KNO3 which could be crystallized by cooling
each solution to 30° C. and the KCl concentration of the resulting
mother liquor are shown in Table 8.
The results from two reactor sam­
ples withdrawn during Run 0-1 have been included.
As seen from Figure 13, the solubility of KCl, Point A, is 27.5%
or 0.275 gm/gm of solution at 30* C.
This is greater than any of the
values which would be experienced upon cooling to 30° C.
Therefore,
no KCl would be crystallized from any of these solutions when they
were cooled to 30° C.
From each of these solutions .more KNO3 could be crystallized,
upon cooling to 30° C., than is reported as being in the solution.
This is due to the fact that at 30° C. the mutual solubility of KNO3
solutions of these acid-water ratios and KCl contents is negative.
Tables 9, 10 and 11 show the results of Runs D-3, D-4 and D-5.
These runs were carried out with the packed column in place and the
results of Runs D-3 and D-4 indicate that the packed column did reduce
the loss of Cl~ to the condensate.
However, the respective values of
16.0% and 12.2% for loss of the CI" in the condensate are still too
large.
These losses indicate that a more effective contacting device
or more reflux is needed.
In Run D-4 an unexplainable low recovery
of K+ ion was observed.
In Run D-5 19.1% of the CI" which was charged to the reactor was
68
Table 8.
Potassium salts concentration in sample
Experimental
From plot
gm KCl
gm KNO3 gm KNO3 Gm KCl/
gm Sol'n gra sol'n cryt. on Sol'n gm
cooling on coolto 30° C/ing to
gm Sol'n 30° C.
Sample
gm HNO
gm H2O
I Run 0-2
0.362
0.116
0.451
0.527
0.245
II Run 0-2
0.399
0.110
0.459
0.522
0.230
III Run 0-2
0.319
0.117
0.350
0.409
0.198
IV Run 0-2
0.374
0.108
0.388
0.416
0.185
I Run 0-1
0.341
0.112
0.446
0.513
0.230
II Run 0-1
0.331
0.161
0.204
0.306
0.232
found in the condensate and only 40% was lost in the noncondensables.
The run was carried out at 35 mm Hg and 192° F. as opposed to about
70 mm Hg and 220° F. for the other runs.
condensate is rather high.
This loss of Cl~ to the
The fact that total losses of CI" and H+
of only about 40% in each case, occurred indicated that the rate of
generation of NOCl and Cl2 was low.
For every mole of KNO3 produced one mole of CI" has to be re­
moved from the system, otherwise the CI" concentration will build up
until KCl is crystallized with the KNO3.
As the only provision for
removing Cl~ from the system is as CI2 and NOCl, the rate of generation
of these gases indicates the rate of production of KNO3.
69
Table 9.
Material balance for Run D-5
Amount, moles
Item
CI"
NO?"
Y
H+
K+
Condensate
1.572
1.2746
2.8403
0.00
Wash from crystals
0.6042
0.8717
0.6638
0.8120
Supernate from crystals
2.065
0.8942
2.2886
0.7097
Crystals
6.950
6.950
Reactor residue
0.6365
1.155
0.8114
0.9412
Sample
0.1058
0.3886
0.1325
0.3596
Total accounted for
4.9835
11.534
6.7366
9.7725
Total added
9.850
13.00
13.00
9.850
Percent recovered
50.59
88.72
51.82
99.21
Table 10.
Material balance for Run D-4
Amount, moles
Item
CI"
N03"
H+
Condensate
1,.432
1..274
2,.805
Wash from crystals
0,.2916
0,.6510
0..4018
0.,5633
Supernate from crystals
2,.477
1..650
3..361
0.,8870
—
3..833
—
3.,833
Reactor residue
1..092
2..981
2,.200
2..5166
Samples
1,.010
2..492
1,.353
2.,161
Total accounted for
6,.393
10.,122
9.,961
Total added
11,.76
12..880
15..50
15,.50
11.,76
Percent recovered
54,.36
83..09
65,,30
84.,70
Crystals
I
K+
--
70
Amount, moles
Item
CI"
NO3-
H+
Condensate
1.592
0.8971
2.588
Wash from crystals
0.5421
0.6622
0.6546
1.198
—
4.941
—
4.941
1.820
0.9095
2.202
0.6005
Supemate from crystals
Crystals
Reactor residue
I
Sample
1,111
1.914
1.4644
1.657
Total accounted for
5,064
9.324
6.908
8.397
Total added
8.346
11.02
11.02
8.346
Percent recovered
60.68
84.64
62.71
100.6
A knowledge of the rate of the reaction was desired.
The most
direct method of measuring the reaction rate seemed to be to measure
the rate at which gas was generated.
the rotameter was added to the system.
It was for this purpose that
Because the system operated
below atmospheric pressure it was expected that air would leak into
the system.
This was found to be true when samples of the gas were
analyzed by gas chromatography.
In order to find the product gas flow
rate it was necessary to measure the total flow rate and multiply it
by the percentage N0C1 and Cl^.
Figure 20 relates rotameter reading and flow rate for a 50-50
mixture of CI2 and N0C1 at 70° F. and 349 and 700 mm Hg absolute.
Figure 20.
Rotameter reading for various flow rates of 50-50 mixtures
of CI2 and N0C1 metered at 700 mm Hg abs., 70° F. and at
349 mm Hg abs. 70° F. reported as cc/min of N0C1- CI2 at
75° F., 750 mm Hg abs.
Figure 21.
Rotameter reading at various flow rates for air metered
at 700 mm Hg, 70° F. and at 349 mm Hg 70° F. reported
as cc/min of air at 75° F., 750 mm Hg
I
72
700 mmHg
Q 10
W
lii
1000
2000
FLOWRATE
o
3000
OF
4000
5000
6000
7000
8000
5 0 % - 5 0 % CI 2 -NOCI MIXTURE, cc /mm.
349 mmHg
700 mmHg
UJ
UJ
1000
2000
3000
4000
5000
FLOWRATE OF AIR, c c / m i n .
6000
7000
8000
73
Figure 21 shows the same type of calibration curves for air.
All of
these curves were calculated from information given in Fischer §
Porter catalog 10A910 (21), and are not based on experimental data.
To use the curves the flow rates were estimated by reading the rota­
meter and then on the basis of gas composition interpolating between
the two curves for a given pressure.
Run D-4 was made at a reactor pressure of 700 mm Hg pressure
and temperature, of 226° F., which was the boiling point of the solution
at this pressure.
Gas samples were taken and analyzed at the same time
liquid samples were withdrawn.
H+ and K+ ions.
The latter were analyzed for NO3-, CI",
I
From the gas analyses and the rotameter readings the
rates were established.
A correlation between reaction rate and composition of the reactor
solution was attempted.
It was found that the rate did not correlate
with any of the individual ion concentrations.
Figure 22 shows the
reaction rate plotted against the H+ ion concentration.
The rate
correlated no better with either CI" or NOj- concentration. The rate
given here is the average flow rate of CI2 and N0C1 in moles per hour
liter of liquids.
This is a measure of the rate at which the following
reaction occurred
3KC1 + 4HN03 = CI2 + N0C1 + 2H20 + 3KN03
Following this initial attempt at finding a correlation between
rate and composition an attempt was made to find a relationship of the
type
R = K (Cl")a (H'+)B (N03")C
74
by regression analysis, where;
(1) R = the rate of the reaction
3KC1 + 4HN03 = 2H20 + Cl2 + N0C1 + 3KN03
in moles/(Hr) (liter of solution)
(2) K = the rate constant
(3) a, b and c are constants
The relationship was written in the form
log R = log K + a log (Cl") + b log (H+) + c log (NO^-)
Values of log K, a, b, and c for the data taken in Run 0-4 were found '
by the method of least squares as shown in Ostle (35).
The relation found in this manner is
R = 1.70 X 1010 (Cl-)"4,7 (H+) 9,4 (NO~3)6,4
The calculations are outlined in the appendix.
Figure 23 is a plot of the above equation.
It can be seen that
this experimental data do not fall very close to the line.
Also the
exponents are too large and the negative exponent for CI" concentration
is questionable.
Because of the negative exponent the relationship
gives the nonsensical predication that if the CI" concentration were
allowed to go to zero while the other concentrations remained above
zero the reaction would proceed at _n infinite rate.
From the above
it seemed logical to assume that the data did not fit a line of the
type
R = K (Cl")a (H+)b (N03~)c
The rate was then plotted against the factor
Figure 22.
Reaction rate plotted against (H+) for Run D-4, 226° F.
Figure 23. 'taction rate as a function of the concentration factor
(H+)9.4(NC)~3)6,4(Cl~y41data and least squares line
through the origin, data from Run D-4, at 226° F.
76
02•
0065
0070
0 075
0080
0.085
0.090
H+ , MOLE FRACTION IN REACTOR
09
|
08
07
< 0.6
0.5
C 04
03
0.2
0.0
1X10
2X10"" 3XI0-11 4XlO*tl 5X10"
REACTOR CONCENTRATION
6X10*11 7X10" exio"11 9X10*" 10X10"
[ci-]"4'7,mole fractions
[H+]9'4 [NO'J6'4
77
(ii+)a(N03-)b(Ci")c
arbitrarily assuming whole integers for the exponents.
While this is
only a search method, it removes the restrictions that the line pass
through (0,0) and that the line be straight.
This allows for the
possibility that the reaction may fall to zero before the concentra­
tions reach zero.
Figure 24 shows the rate plotted against the factor (H+)(C1~),
Figure 25 against the factor (H+)2(C1")(N03~), and Figure 26 against
the factor (H+)3(C1')2(N03"). Figure 26 seems to be the most satis­
factory curve.
A smooth curve can be drawn through most of the points.
Through part of the points a straight line can be drawn.
For this
straight line portion of the curve the following relation can be
written
R = 8.13 X 107 (H+)3(N03)(CI-)2 - 1.59 X 10"7
However this relationship cannot be used with confidence outside of
the interval over which the plot is linear.
Figure 26 shows the rate
for Run 0-5 plotted against the factor (H+)3(C1")2(H+): These data
were taken at a pressure of 349 mm Hg absolute and 192° F.
The factor against which the reaction was plotted in Figure 26
seemed to involve many more elements than would enter into the rate
controlling step of a reaction, six.
However, it may be that two
moles of HC1 react with one mole of HN03.
If this were true, a factor
such as the one used would be necessary.
Comparison of Figure 26 with Figure 27 will show that the
Figure 24.
Reaction rate fqr Run D-4 against the concentration
factor (H+)(C1"), 226° F.
Figure 25.
Reaction rate for Run D-4 plotted against the concentra­
tion factor (H+)2(C1-)(N0-3), 226°, F.
4 0XI0*3 4 2X10*' 44X10® 4.6XI0"3 4.8X10"' 5.0Xio" 3 S.ZXIO"3 5.4XI03 5.6X10 3 5.8X10 3 6.0X10*
REACTOR CONCENTRATION [h*] [ci"] , mole fractions
1.0
X 0.8
0.6
<
<z
Z 04
o
t—
o
<
UJ
o: o.2
4.0XIO"5 4.2 X 10"® 4.4X10"® 4.6XIO'9 4.6XIO"5 5.0XIO"5 5.2XIO"5 5.4XI0*5 5.6XIO"5 5.6XIO"5 6QXI0"5
REACTOR CONCENTRATION [H + ] 2 [cr] [N0" 3 ] , mole froctions
80
reaction rate falls off sharply as the temperature is decreased.
This
is true even though lower pressure accompanies the lower temperature.
This lower pressure might cause the gas to be more readily removed
from the reactor.
Even so, the reaction was much slower at the lower
temperature.
The possibility that the gas composition could be varied from the
mole ratio of Cl2 to N0C1 of unity did not seem too great.
However, if
it were possible to increase the ratio it would reduce the expense of
processing the N0C1.
This would make any process much more attractive.
Studies were made at 192° F. and 226° F. to determine if changing the
ratio of acid to chloride changed the gas composition and also to see
if the reaction rate changed the gas composition.
shown in Figures 28 and 29.
higher C12/N0C1 ratio.
The results are
Only one point showed a significantly
This point was at a very low gas flow rate.
The samples at low reaction rates contained small amounts of Cl2 and
NOC1 relative to the amount of air present and therefore analysis was
less reliable.
Figures 28 and 29 show no correlation between acid
chloride ratio and gas composition.
Neither do they show a correlation
between reaction rate and gas composition.
By examining the data it
can be seen that there is no significant change in gas composition
when the temperature is changed from 192° F. to 226° F.
Figure 26.
Reaction rate for Run D-4 plotted against the concentration
factor (H+)3(N0-3)(C1-)2, 226° F.
Figure 27.
Reaction rate for Run D-5 plotted against the concentration
factor (H+)5(N0'3)(C1-)2, 192° F.
I
82
!.0|
1.6XICT7
1
1
1
!
!
r
1.8XIO'7 2.0XIO*7 2 2XIO"7 2.4XIO"7 2.6XI0-7 2.8XI0"7 3.0XI0*7 3.2XI0"7 3.4XI0"7 36XIO*7
REACTOR CONCENTRATION, [h + ] 3 ^0"^[c I '] 2 mole froctions
4.0
3.6
32
= 2.8
2.0
0.8
0.4
0.0
4X LO-7 8XIO-7 12XIO"7 I6XI0"7 20XKF7 24XKF7 28X10"
REACTOR CONCENTRATION [H]![CI]Z[N03] , mole fractions
Figure 28.
Gas composition plotted against acid:
in the reactor at 192° F. and 226° F.
chloride ratio
Figure 29.
Gas composition plotted against reaction rate at 192° F.,
and 226° F.
84
2.8-
1
r
o 2.4o
z
O 192" F
O 226"F
o
E 2.0F
_CM
O
<o 1.6-
o
E
z*
O 1.2-
O
o
O o
V)
™£T
O
CL 0 . 8 2
O
O
CO
O 0.4}-
^ô™
e
0.9
_L
1.0
1.1
1.2
1.3
I
1.5
1.4
1.6
J
1.7
L
1.8
1.9
REACTOR CONCENTRATION, moles acid/mole Cl*
2.8
1
i
1
1
o
O
O 192* F
S 226*F
-0
1
fvl
O
1.6
o
E
.
z 1.2 —
o
to
O
CL 0.8
S
o
o
•
e
0
0
6
o
e
O
0
•
co
< 0.4
O
e
1
0.1
1
0.2
.
1
0.3
REACTION RATE, moles/hr.
1
0.4
-
0.5
85
PROPOSED PROCESS
Cost Analysis for Commercial Process
A preliminary cost analysis was made for the process.
This cost
analysis, for a plant at Houston, Texas, indicated that the cost of
plant nutrients as KNO3 would be about twice as much as the same plant
nutrients would cost if purchased as KC1 and NH4NO3.
However, this
is not a detailed cost estimate and upon a thorough study of the
process it might be found that the KNO3 would not be this expensive.
Also, as was noted in the literature survey, certain crops are
damaged by excessive chloride ion concentration, and a premium for
potassium, which does not contain chloride, might be in order.
The capital investment per annual ton of plant capacity was
extimated from an article which appeared in the May, 1951, Chemical
Engineering magazine (47).
This cost was considered to be similar
to the cost of plants for the manufacture of other inorganic chemicals
such as soda ash, calcium cyanamide and sodium bichromate.
$61.50 per annual ton of KNO^ was chosen.
A cost of
The cost was then changed
from the 1950 value to today's cost, $110.07/ton, using the Engineering
News-Record (ENR) Construction Cost Indices of 510 for 1950 (17) and
920.1 for February, 1964 (18).
The capacity of the plant would be 100
to 200 tons KNO3 per 24-hour day.
The raw material costs as well as the comparative costs for
bagged NH4NO3 and KC1 were obtained from the May 16, 1964, Oil Paint
86
and Drug Reporter (16).
The conversion was estimated to be 97%.
The
labor requirements were estimated from an article by C. H. Chilton
which appeared in the February, 1951, Chemical Engineering (15).
An
article by S. P. Smith in the March, 1953, Chemical Engineering (42)
was used to estimate the shipping costs.
The working capital was
estimated at 15% of the fixed capital costs or $16.59/annual ton of
KN03 capacity.
The projected price for KNO3 is $125.20/ton or $125.20 per
277 lb of N and 933 lb of K^O.
These nutrients could be purchased as
827 lb of bagged NH4NO3 (33.5% nitrogen) at $70.00/ton for $28.92 and
1,555 lb of bagged KC1 (60% of K^O) at $39.50/ton for $29.00 for a
total of $58.02.
The KC1 price includes an $8.00/ton freight dif­
ferential which a southeast U. S. consumer might expect to pay for
KC1 from Carlsbad, New Mexico, as opposed to KNO5 from Houston, Texas.
A product which costs twice as much as competitive products should
not be expected to replace the less expensive items except where these
are mitigating circumstances.
condition exists.
In the production of tobacco, such a
Nevertheless, it would seem that with such a price
differential a tobacco grower who needed K20 would apply as much in the
chloride form as he could by law or as much as he could without changing
his product so that he would receive a lower market price.
K20 might be applied as KNO3.
Additional
Perhaps KNO3 will find its greatest
consumption in mixed fertilizers which also contain the permissible
amount of KC1.
87
Table 12.
Production cost estimate for KNO3 at Houston, Texas
Item
DIRECT COSTS
Raw materials
KCl as K9O
Freight from
Carlsbad, N. M.
HNO,, 100%
Freight, local
Units/ton KNO5
Cost/unit
Cost/ton
KNO?
48.05
$0.40 unit
$19.22
0.825 tons KCl 10.00/tonKCl
0.644 tons
78.00/ton
0.963 tons 60% 6.00/ton
8.25
50.15
5.677
HNO3
Labor
Operators •
Supervisors
Services
Power
Steam
Water
Maintenance
(5% of fixed capital
investment
Packaging
INDIRECT COSTS
Depreciation (10% of
fixed capital investment
Taxes and insurance (5% of
operating labor)
Plant overhead (50% of
operating labor)
TOTAL PRODUCTION COST
2.0 hr/ton
0.25hr/ton
2.50/hr
3.25/hr
5.00
0.81
0.70
0.65
0.08
24 bags
0.15/bag
5.50
3.60
11.01
0.25
2.50
$113.39
88
Table 13.
Percent return on investment for KNO3 plant at Houston,
Texas
Item
Selling price
KNO3 $125.20/ton
CI2 $3.25/100 lb
Total sales
$125.20
22.90
$148.10
704 lb/ton KNO3
Production cost
Gross profit
-113.39
34.71
Administration, 7% of sales
-10.36
Net profit before income tax
24.35
Federal income tax (48% of net profit)
-11.68
New earnings
12.67
Percent return on investment
New earnings
(fixed capital + working capital)
_
, 12.67
_
110.07 + 16.59 "
Corrosion Study
The corrosive nature of aqua regia is well known.
Very similar
conditions will occur in a reactor built to react KCl with HNO3 and
corrosion difficulties may develop throughout a plant built to produce
KNOg.
Kobe (27) states that many corrosion problems are inherent in
Solvay Process Company's sodium nitrate process.
Previous to the construction of a pilot plant, a study of possible
materials of construction is necessary.
A corrosion study to find
89
materials of construction suitable for the various pieces of equipment
is recommended.
Pilot Plant
In the recommendations section is a suggestion that a pilot-plant
be constructed.
This step would follow development of a method for
treating the reactor off gas to recover Cl2 and the nitrogen oxides as
HNO3.
A possible flow sheet for the pilot plant is shown as Figure 30.
This pilot plant should be constructed so it could operate continuously
at pressures both above and below atmospheric.
As is shown in the flow sheet, three control devices are needed.
The steam flow rate to the reactor jacket should be controlled in order
to maintain the temperature and thereby the concentration constant.
The liquid draw from the reactor should be controlled in order to
maintain the liquid level.
The gas flow rate to the gas treatment
plant should be controlled in such a manner as to maintain the reactor
pressure constant.
The amount of materials fed to the reactor should be controlled
quite carefully as must the amount of wash water used.
At steady state
the amount of materials removed from the system as gas, condensate and
in the solid KNO3 product should equal the feed.
any materials should occur.
Thus no build up of
Figure 30.
Flow sheet for proposed pilot plant
VAPOR
LINE
£
60% HNO
FEED
PUMP
CONTINUOUS SOLID
KCl FEEDER
RACKED
SCRUB
COLUMN
NOCI AND CI,
PRESSURE
REGULATOR
TO GAS TREATMENT
PLANT
CONDENSER
WASH WATER
COOLING
WATER
—>
RECORDER!
MOTHER LIOUOR
t RETURN TO REACTOR
Y
CRYSTALLIZER
FLOW
RECORDER
RECORDER
CONDENSATE
• PURGE TO REMOVE IMPURITIES
TO DRYING
AND BAGGING
TANK
ISTEAM
O
REACTOR
HgO PURGE
TO DRAIN
LIQUID
DRAW
CENTRIFUGE
DIAPHRAGM r-"-i
PUMP
I
I
WET
%N0 3
92
CONCLUSIONS
1.
A batch process does not produce pure KNO3.
the product contained KCl as well as KNO3.
In batch processes
This was true if the flask
containing the acid and KCl was placed in a constant temperature bath
or if the contents were heated to dryness.
2.
The solubility data which were taken indicate that a continuous
fractional crystallization process is possible.
The solubility of
KCl in aqueous nitric acid solutions at 30° C. is high whereas the
solubility of KNOg.under similar conditions is quite low.
3.
The continuous process gave encouraging results.
A continuous
fractional crystallization process resulted in a solid product which
was pure KNO3.
4.
The reaction rate is a function of temperature.
Increasing the
reaction temperature from 192° F. to 226° F. increased the reaction
rate quite significantly.
5. The reaction rate increases with concentration.
Below a threshold
concentration the rate is insignificant. However, at 226° F., over a
limited concentration range the rate increases as a linear function
of the factor (H+)3(C1')2(N03-).
6.
The gas composition ratio of CI2 to NOCI was not a function of
acid to chloride ratio over the range studied.
Neither was the gas
composition found to be a function of temperature or reaction rate.
7.
NOCI can be converted to NOg and CI2 by reacting it with hot
93
concentrated HNO-.
8.
NOCI can be reacted with Mn02 in hot nitric acid to give Cl2 as the
gas product.
94
RECOMMENDATIONS
1.
It is recommended that a corrosion study be made in order to deter­
mine what materials would be suitable for construction of the reactor,
the crystallizer, the column, and the condensers and to determine what
materials would be suitable for piping and other necessary construc­
tion.
2.
It is "recommended that a study be conducted to determine the best
way to treat the affluent gas in order to separate the Cl2 and NOCI
and convert the NOCI into commercially valuable forms.
3.
It is recommended that following the completion of the projects
mentioned above that a pilot plant be constructed.
95
LITERATURE CITED
1.
Baniel, Abraham and Blumberg, Ruth. Preparation of watersoluble inorganic metal salts and HC1 acid by double
decomposition. U. S. Patent 3,894,813. July 14, 1959.
2.
Bayer, Ernst. Gas chromatography. New York, New York,
Elsevier Publishing Company. 1961.
3.
Beekhuis, Herman A., Jr. Absorption of nitrogen peroxide.
U. S. Patent 2,296,328. Sept. 22, 1942.
4.
. Process for oxidizing nitrosyl chloride.
Patent 2,297,281. Sept. 29, 1942.
U. S.
5.
. Process for the decomposition of nitrosyl chloride.
U. S. Patent 2,138,017. Nov. 29, 1938.
6.
. Process for the production of a nitrate.
Patent 2,215,450. Sept. 24, 1940.
7.
. Process for the production of a nitrate and chloride.
U. S. Patent 2,138,016. Nov. 28, 1938.
8.
. Process for the production of chlorine and a nitrate
from nitrogen peroxide and a chloride. U. S. Patent 2,296,762.
Sept. 22, 1942.
9.
. Process for the separation of nitrosyl chloride and
chlorine. U. S. Patent 2,247,470. July 1, 1941.
10.
. Process for the treatment of mixtures of nitrosyl
chloride and chlorine. U. S. Patent 2,150,669. Mar. 14, 1939.
11.
. Process for treating mixtures of nitrosyl chloride
and chlorine. U. S. Patent 2,130,519. Sept. 20, 1938.
12.
. Production of alkali and alkaline earth metal nitrates.
U. S. Patent 2,148,429. Feb. 28, 1939.
13.
. Production of nitrates for nitric acid and chlorides.
U. S. Patent 2,269,000. Jan. 6, 1942.
14.
. Recovery of alkali metal nitrates.
2,124,536. July 26, 1938.
U. S.
U. S. Patent
96
15.
Chilton, Cecil H. Process labor requirements. Chemical
Engineering 58, No. 20: 151. February, 1951.
16.
Current market quotations. Oil Paint and Drug Reporter.
No. 11: 11-31. March 16, 1964.
17.
Dryden, Charles E. and Winfield, Michael D. Chemical engineering
costs. Columbus, Ohio, The Ohio State University, 1963.
18.
Economic indicators.
March 16, 1964.
19.
Epshtein, D. A. and Nikonova, N. I. Reaktziy vodorastrorimych
solei s paroobranznymy vestchestvamy i prisutuii vodianoho
para. In Bordin, I. P., ed. Issledovaniya po prikladroy
chimii. pp. 50-57. Moscow, Akad. Nauk S. S. S. R. 1955.
20.
Fast push to fill chlorine need.
76, 79. July 7, 1962.
21.
Fischer and Porter Company. Handbook: application, sizing
and calbration prediction data. Catalog 10A9010. Hatboro,
Pa., Author. 1959.
22.
Fogler, M. F. The salt process for chlorine manufacture. In
Sconce, J. S., ed. Chlorine; its manufacture, properties and
uses. pp. 235-249. New York, New York, Reinhold Publishing
Corporation. 1962.
23.
Isbell, Raymond E. Determination of hydrogen cyanide and
cyanogen by gas chromatography. Analytical Chemistry 35:
255-256. 1963.
24.
Jacob, K. D. Nitrate of potash; a new product for the industry
in production at Vicksburg plant. Commercial Fertilizer 103,
No. 11: 23-25. Nov. 1963.
25.
Jacobs Engineering, primes for new growth. Chemical and
Engineering News 41, No. 8: 34, 36. Feb. 25, 1963.
26.
Kirk, Raymond E. and Othmer, Donald P. Encyclopedia of chemical
technology. Vol. 2. pp. 26-27. New York, New York, The
Interscience Encyclopedia, Inc. 1953.
27.
Kobe, Kenneth A. Inorganic process industries.
New York, The Macmillan Company. 1948.
185,
Chemical Engineering 71, No. 6: 255.
Chemical Week 91, No. 1: 75,
New York,
97
2ti.
Lovell, Clarence E. and Lewis, Clifford Jackson. Production of
alkali metal nitrates from alkali metal chlorides. U. S.
Patent 2,916,353. Dec. 8, 1959.
29.
McCants, C. B. Potassium nitrate in crop production.
tural Chemicals 16, No. 1: 30-32, 78-79. 1961,
30.
Mehring, Arnon L., Ross, William H. and Merz, Albert R. Prepara­
tion of potassium nitrate. Industrial and Engineering Chemis­
try 21: 379-382. 1929.
31.
Miller, Ralph. Production of chlorine and metal nitrates.
Patent 2,691,569. Oct. 12, 1954.
32.
Mirkin, I. A« Preparation of potassium nitrate by the action of
nitric acid or nitrogen oxides on the chloride. (Translated
title) Khimicheskaya Promyshlennost S. S. S. R. 8: 351-359.
1931. Original not available; translation secured from Photoduplication Service, Library of Congress Document 59-10738.
1959.
33.
Nelson, E. L. Determination of total nitrogen in materials con­
taining nitrate: reduction by chromous ion. Journal of the
Association of Official Agricultural Chemists 43: 468-472.
1960.
34.
Nikonova, I. N. and Epshtein, D. A. 0 mechanizme; kinetike
reaktsiy vodorastvorimych solei s paroobraznymy vestchestuamy
i prisutuii vodiancho para. Doklady Akad Nauk S. 5. S. R.
86: 353-356. 1952.
35.
Ostle, Bernard. Statistics in research. 2nd ed.
The Iowa State University Press. 1963.
36.
Potassium nitrate plant goes on stream. Chemical and Engineering
News 41, No. 44: 32, 33. Nov. 4, 1963.
37.
Runge, Henner. Gaschromoatographische Analyse anorganischer
Case. Fresenius* Zeitschrift fur Analytische Chemie 189:
111-124. 1962.
38.
Russel, Sir Edward John. Plant nutrition and crop production.
Berkeley, California, University of California Press. 1926.
39.
Sakaida, Roy R., Rinker, Robert G., Cuffel, Robert F., and
Corcoran, William H. Determination of nitric oxide in a
nitric oxide-nitrogen system by gas chromatography. Analytical
Chemistry 33: 32-34. 1961.
Agricul­
U. S.
Ames, Iowa,
98
40.
Sauchelli, Vincent. The chemistry and technology of fertilizers.
New York, New York, Reinhold Publishing Corporation. 1960.
41.
Scott, R. P.
Gas chromatography.
London, Butterworths.
42. Smith, Stuart P. If you ship your products.
60, No. 3: 222-225. March, 1953.
43.
1960.
Chemical Engineering
Stengel, L. A. Process for separating nitric acid\from a mixture
"containing nitric acid and hydrogen chlorine. U. S. Patent
2,555,278. May 29, 1951.
44.
. Production of alkali metal nitrates.
2,535,989. Dec. 26, 1950.
U. S. Patent
45.
. Separation of hydrogen chloride from nitric acid.
U. S. Patent 2,590,028^ March 25, 1952.
46.
Talbot, P. J. and Thomas, J. H. The reaction between hydrogen
chloride and nitrogen peroxide. Transactions Faraday Society
55: 1884-1891. 1959.
47.
What price process plants?
164-165. May, 1951.
48.
Whitnack, Gerald C. and Holford, Clifford J. and Ganz, B. St.
Clair and Smith, B. L. Determination of nitric oxide and
nitrogen teroxide in a mixture. Analytical Chemistry 23:
464-467. 1951.
Chemical Engineering 58, No. 5:
49. Wolf, Freidrich and Schier, Karl Heinz. Uber die Analyse von
NC>2, N0C1 and CI2 in Gasgemischen. Zeitschrift fur
Chemie 1: 216-217. 1961.
99
ACKNOWLEDGMENTS
The author wishes to express his gratitude to Dr. George Burnet
who suggested the problem and guided the investigation.
The author also wishes to express his appreciation to the
National Science Foundation for its financial support, through a
Cooperative Fellowship.
Finally the author wishes to thank his wife, Jorene, who sup­
ported this work in numerous ways.
100
APPENDIX A.
NELSON'S METHOD FOR
DETERMINATION OF NITROGEN
Nelson has suggested a method for analysis of solutions for total
nitrogen (33).
This method which employs a chromous solution to
reduce nitrate
8Cr++ + N03" + 10H+ = 8Cr+++ + NH4+ = 3H20
in an acid solution is more suitable for some solutions of N0g~ in
H2SO4 than Kjeldahl methods which reduce the nitrogen in a basic
solution.
Nelson suggests the following procedure:
Apparatus and Reagents
,
(a) Chromous solution reductor - See Figure 31. Con­
sists of 2 L aspirator bottles, one a reductor and the other
a solution reservoir; an automatic 50 ml pipet; and a source
of nitrogen or other inert gas. The reductor contains 2 Kg
amalgamated Zn and is closed with a 2-hole rubber stopper
through which is inserted a 3-way stopcock and a vent tube
connected to a water sealed trap. The solution reservoir
is closed with a one-hole rubber stopper through which is
inserted a 3-way stopcock. Connections between the bottle
and pipet are made with Tygon tubing. Break off the original
tip of the pipet to permit a fast delivery and replace with
an 11" extension (the pipet should deliver 50 ml in 17
seconds or less).
(b) Amalgamated zinc. -- Place 2 Kg reagent grade mossy
Zn in a 4 L beaker and add 1700 ml of 1+ 1 HC1 containing
27.6 g HgClg* Let the Zn amalgamate for about 5 minutes
while stirring with a heavy glass rod. Decant the acid and
wash the Zn four times by décantation with distilled water.
Transfer the zinc to the reductor (Figure 2).
(c) Chromous solution, IN (2.7N with sulfuric acid).
—Dissolve 267 g CrClj. 6H^O in 805 ml (by graduate) of
water to which 70 ml concentrated H2SO4 has been added and mix.
Figure 31.
Apparatus for preparation of chromous solution. 1: 250 ml Haberman bulb, 50 ml of
water. 2: 250 ml Haberman bulb trap. 3: 3-way stopcock with plug clamp. 4: re­
ductor ; 2 L aspirator bottle. 5: 3-way stopcock with plug clamp. 6: chromous
solution storage; 2 L aspirator bottle. 7: 50 ml automatic pipet with 11 inch
glass tube extension. 8: 250 ml beaker for overflow and seal against air. Con­
nections are of Tygon tubing. Connections between the bottles should be long
enough to permit shaking of the reductor by hand to promote a rapid reduction if
desired (33)
m
ii
: Il
il
w
III
2
« A
^ 6 Q Q*
û o'»ti
*» «
0 on "DO"
%:%Y;
=C
a <> o <Ï 0
Amalgamated
zinc
103
Pour the solution into the reductor, (lower outlet tubing is
clamped off) stopper, and close the 3-way stopcock to the
reductor. The solution will reduce in about 3 hours, chang­
ing from a dark green color to the characteristic sky blue
of the chromous ion. A small amount of hydrogen is evolved
and vented through the Haberman bulb traps. Oxygen from air
above the solution is of no consequence, as it will be con­
sumed in the reduction.
. I
Purge the solution reservoir and pipet with nitrogen.
Transfer the reduced solution under about 3 lbs. of nitrogen
pressure to the reservoir. During the transfer the reductor
vent is clamped, the lower outlet tubing is undamped, the
automatic pipet is closed, and the storage bottle is vented
to permit the solution to flow. After the transfer, clamp
the reductor outlet, unclamp the reductor vent, and position
both 3-way stopcocks to apply 3 lbs of nitrogen pressure to
the reservoir for filling the pipet. Nitrogen pressure is
unnecessary during idle periods of the apparatus. A small
flow of nitrogen is maintained over the top of the automatic
pipet during dispensing. If air should accidentally gpt into
the reservoir bottle and oxidize the solution it can be
transferred back to the reductor with nitrogen pressure.
Additional chromous solution can be prepared in the reductor
while that in the storage bottle is being used. If the
amalgamated zinc becomes inactivated, treat it with 1+1 HC1
for 5 minutes and then wash four times with distilled water.
(d) Aludum boiling stones. — Norton 14X (A. H. Thomas
Cat. Code UEVOR).
Determination
Nitrogen fertilizer solution samples—Pipet a 25 ml
aliquot of appropriately diluted solution to contain 0.061
g or less of nitrate nitrogen (0.35 g NH4NO3) into a 650 ml
Kjeldahl flask. Wash down any sample adhering to the sides
of the flask with 2-3 ml distilled water, (solutions con­
taining no free ammonia may be weighed directly into the
flask and then diluted with 25 ml distilled water.)
Add 50 ml IN chromous solution from the apparatus shown
in Figure 2. The extension tip of the automatic pipet should
be positioned about 1" above the surface of the sample solu­
tion during the addition so as to minimize exposure of the
reagent to the atmosphere. Swirl to mix and let stand for
about 1 minute or longer. Add 25 ml coned H2SO4 and 2-3 g
boiling stones, and swirl to oxidize any residual chromous ion.
104
Place the flask in an inclined position of about 15°
from horizontal on a heater (preheated if electrical; do
not use asbestos ring or wire gauze with heater) and digest
at full heat. Remove the flask from the heater when the
chromic sulfate is precipitated as a rose-colored insoluble
form which causes bumping of the solution. Do not turn off
the heat and leave the flask to cool on the heater at this
point, as the solution may bump severely enough to cause
the flask to jump and break against the heater. Fuming
will continue about 4-6 minutes, which will convert ures
nitrogen completely to ammonium sulfate.
Cool the flask and add 200 ml distilled water. Cool to
room temperature or below and add 2-3 g 20 mesh zinc and 100
ml 50% ,NaOH solution. Tilt the flask to layer the NaQH
underneath the acid mixture. Connect the flask immediately
to a condenser, mix thoroughly, and distill the ammonia (200
ml distillate is sufficient) into 40 ml 0.5N standard acid
contained in a 500 ml Erlenmeyer flask. Add 6-9 drops methyl
red indicator and titrate the excess acidity with 0.25N NaCH.
Correct the titration for nitrogen contained in the reagents
by making a blank determination.
When analyzing three samples of NaNOg Nelson found a mean recovery
of 99.90% with a standard deviation of 0.035% and a standard deviation
of the mean of 99.90 + 0.020.
105
APPENDIX B.
WOLF AND SCHIER GAS ANALYSIS
In the reaction of KC1 and HNOg,
3KC1 + 4HN03 = Cl2 + N0C1 + 3KN03 + 2H20,
Cl2 and N0C1 are given off as gas.
In the batch studies the method of
Wolf and Schier (49), which was developed for the analysis of N0C1,
N02 and CI2, was used to analyze.the gas evolved.
The gases are bubbled through two vessels which each contain 90%
H2S0 and then through a vessel containing 10% KI solution.
The reac­
tion of nitrosyl chloride is
N0C1 + H2S04 = H Cl + NOHSO4
The nitrogen dioxide reacts as follows:
2NO2 + H2S04 = HNO3 + NOHSO4
The elemental chlorine is only slightly soluble in H2SO4 and
therefore it passes through the acid to react with the KI.
The reaction
products of the nitrogen containing gases are in the H2SO4 solution.
The N02 and N0C1 are then determined by the method of Whitnack et al
(48).
The total nitrogen is determined by the method of Nelson as
outlined above.
Then the trivalent nitrogen (NOHSO4) is determined by
titration with a solution of potassium permanganate using the following
technique.
An aliquot is added to an excess of potassium permanganate.
Then an iron (II) sulfate solution is added until the permanganate that
remains is used up and an excess of iron (II) sulfate is present.
The
excess iron (II) sulfate is then back titrated with permanganate.
A
106
blank should be run. The NO2 absorbed is two times the difference
between the total nitrogen and the trivalent nitrogen.
The chlorine absorbed in the third bottle is then determined by
titrating with Na^SgOg to determine the elemental I2.
107
APPENDIX JC.
OUTLINE OF CALCULATION OF COEFFICIENTS
FOR RATE CONCENTRATION RELATIONSHIP
The values of a, b, c and K were needed for the relationship
R = K(Cl-)*(H+)b(NQ-)C
The relationship was then written in the fonn
log R = log K + a log (Cl~) + b log (H+) + c log (NOj).
The following substitutions were made
X0 = 1
Xx = log (Cl~)
X2 = log (H+)
X3 = log (N03)
Y = log R
b0 = log K
b% = a
b2 = b
b3 = c.
Then the relationship was written in the form
Y =
b0X0 + b^X^ + b2X2 + b3X3
From Run D-4 nine data points were available.
For each of the points
the values of (CI"), (H+) (NO"), and K were known.
The logarithms
of these values were taken giving the values of Xj, X2, X3 and Y for
each data point.
108
Table 14.
Data from Run 0-4
Sample
(CI™), mole
fraction
III
(H+), mole
fraction
(N0g), mole
fraction
0.0692
0.0672
0.1700
0.718
IV
0.0666
0.0689
0.1526
0.545
V
0.0658
0.0700
0.1412
0.396
VI
0.0644
0.0681
0.1361
0.148
VII
0.0649
0.0800
0.1161
0.704
VIII
0.0653
0.0836
0.1110
0.141
IX
0.0640
0.0858
0.1072
0.797
X
0.0637
0.0868
0.1069
0.830
XI
0.0642
0.0868
0.1193
0.663
Reaction rate
moles/(1)(hr)
The logarithms of the values in Table 14 were found and Table 15 was
constructed.
From Table 15 the values needed in the following relationships
were found.
bQ 2 X0X0 + bx 2 XQX: + b2 2 XQX2 + b3 2 X0X3 = 2 XQY
bQ 2 X1XQ + bj 2 XXXX + b2 2
X^X2 + b^ Z X^X^ = 2 XXY
bQ 2 X2XQ + b1 2 X2XX + b2 2
X^Xg +b^2
= 2
X^Y
bg 2 XjXQ + b^ Z
XgX2 + b3 2
^3^3 = 2
X3Y
XjX^ + b2 2
The solution of these 4 equations gave the following:
bg = 10.229301 = logiQ K
bj = -4.701415 = a
109
Table 15.
Logarithms of data for Run D-4
Sample
*0
*1
X2
*3
Y
III
1
-1.15989
-1.17263
-0.76955
-0.14375
IV
1
-1.17653
-1.16178
-0.81645
-0.26328
V
1
-1.18177
-1.1549
-0.85017
-0.40209
VI
1
-1.19111
-1.16685
-0.86934
-0.82962
VII
1
-1.18776
-1.09691
-0.93517
-0.15255
VIII
1
. -1.18509
-1.07779
-0.95468
-0.85140
-1.19382
-1.06651
-0.96981
-0.09832
IX
X
1
-1.19586
-1.06148
-0.97102
-0.08092
XI
1
-1.19246
-1.06148
-0.92336
-0.17836
b2 ='9.36387 = b
b% = 6.374009 = c
Then the rate relationship was written as follows:
R = 1.70 X 1010 (Cl~)~4"^(H+)9,4(NOp 6,4